Overgrown Rover

Overgrown Rover (育ちすぎたポチ, Sodachisugita Pochi; Viz: Overgrown Pochi), also called Rover, is a Dragon-level Mysterious Being and an executive member of the Monster Association. Its role is to guard the Monster Association Headquarters.

After the Monster Association's downfall, it becomes Saitama's pet alongside Black Sperm and is currently entrusted to Forte, Chain'n'toad, and Butterfly DX.

Appearance
Rover is a very large, black, six-eyed dog monster. Its eyes are ruby colored and seem to have a glow. It has very large fangs and four toes per paw. Its fur is very shaggy and roughed up, especially on the outer part, whereas the inner part of its body presents less hair and shows clearly its muscles. It lacks a tongue, and has no visible ears or nose.

After the battle between the Hero Association and the Monster Association, Rover shrinks to the size of a puppy.

Personality
Rover behaves like a guard dog. It is a diligent and loyal protection animal, who instantly tracked down Garou after the Hero Hunter helped Tareo escape and did not stop in pursuing his quarry under any circumstances. However, under intense and traumatic conditioning, it was forced to learn to sit even if the command was given by an enemy

Rover, however, does not instantly grow hostile toward intruders, as it neither attacked nor followed Garou and Tareo in its initial encounter with the pair, leaving them alone when they backed off slowly. Additionally, Rover does not seem to differentiate between friend or foe when angered, as it attacked and killed fellow monster Unihorn after the latter accidentally hit Rover during a fight with Garou.

Rover's canine behavior also means that it can be trained by someone, though they must have enough physical strength to do so. Garou jokingly tells it to sit during their battle before striking it to no effect; however, Saitama did the same and successfully conditioned Rover into obeying the command to "sit", which Bang unintentionally exploited later. It also came to fear Saitama because of this encounter, and disobeyed Orochi's commands choosing to flee instead.

Monster Association Arc
Overgrown Rover encounters Garou and Tareo when the two are trying to escape the Monster Association Headquarters.

After the two slowly sneak away from Rover without provoking it, three other Demon-level monsters, Super Mouse, Showerhead and Unihorn appear and fight the Hero Hunter. Unihorn and his associates use their Trinity Demon Bursting Speed Thrust attack to launch Unihorn at the Human Monster but Garou easily brushes him aside. Sending him shooting into the distance before realizing that it was in the same direction where the Monster Association cadre was, hearing its enraged roar. Unihorn's head is then thrown back all broken up. After a moment, Rover finally joins in the battle and fires an energy core from its mouth. Garou grabs Tareo and narrowly outruns it while the remaining two Demon-level monsters are eviscerated in the blast. Once Garou makes it to the surface, he tells Tareo to run while he handles Rover. The Hero Hunter strikes at Rover's front left leg in an attempt to throw it off balance, but Rover merely shrugs it off and fires another blast at him point-blank. This time, Garou is unable to escape it and is forced to take the full brunt of the assault, destroying several floors of the Monster Association headquarters in the process. When Rover sees the intruder still standing, it fires a rapid barrage of explosive sphere's as it runs across the damaged walls. This time, Garou manages to avoid all of the attacks, and strikes a powerful blow on Rover's snout. However, Rover merely bounces back, literally shaking off the attack coming out completely unharmed, shocking Garou. Rover then bites down on his leg and flails him around like a rag doll before shooting another close-range discharge at Garou, which destroys several more floors of the headquarters. Afterward, Rover stops pursuing Garou and allows Psykos to deal with him. While roaming the Monster Association hideout, Rover encounters the wayward Saitama after he has finished killing a band of monsters. Saitama attempts to offer Rover a bone while asking it for the location of monsters who has caused noises around in return, but Rover simply angrily assaults him with its energy blasts. The bald hero manages to dodge the attack, remarking at its lack of training and wondering if it was one of the things responsible for making the noise. Saitama then tells Rover to sit as he punches it into submission, sending a shockwave throughout the entirety of the Monster Association HQ.

When Saitama meets Orochi, and during the ensuing battle, Rover wakes up. Orochi notices Overgrown Rover is still alive and orders Rover to attack Saitama. The monstrous canine looks at Saitama for a second, but upon seeing him, recognizes its assailant and immediately retreats in terror, surprising Orochi and prompting him to ask Saitama what he did to Rover. Saitama simply tells Orochi that he gave Overgrown Rover a beating, and the two begin their battle. Later, Rover encounters Bang, Bomb, and Fubuki; firing multiple energy blasts at them while in hot pursuit. Despite its injuries from Saitama, Rover continues to pressure its attack on the three outsiders with its lethal energy cores. The latter three manage to hide from it for a time, but Rover quickly catches them by surprise and nearly ends the trio with a sneak attack.

The elder martial artists are saved at the last second via psychic reinforcement by Fubuki whom suggest they use their newfound vigor to retreat while they still can. As Rover proceeds to attack by firing multiple energy balls at them, Fubuki charges towards the enery spheres in an attempt to deal with them on her own, but the two martial artists appear in front of her and deflect them away, protecting her. They later use their combination attack Cross Fang Dragon Slayer Fist on the dog-like monster. Despite their best efforts, Rover still survives their onslaught without visible injuries. Out of annoyance, Bang rhetorically asks why Rover couldn't simply be quiet and sit down. Rover, remembering being forced into submission by Saitama after he gave the same command, obediently sat and stopped the fighting.

For the remainder of the invasion, Rover's enormous size begins to reduce drastically until it became no bigger than an average dog due to the damage he took from his multiple battles.

Psychic Sisters Arc
After the destruction of the Monster Association, Rover encounters Saitama again, but instead of killing the former monster he merely lifted it, mistaking it for a lost dog. Black Sperm, watching them, then decides to follow Saitama as well, thinking that his chances to survive were bigger with him, and together, he and Rover persuade Saitama to take them to the Hero Association's headquarters in A-City, which the hero only begrudgingly accepts.

At the entrance, however, the security system recognizes Rover and Black Sperm as monsters and sends defensive robots to deal with them. Black Sperm hides behind Rover, who growls at the robots and they then witness Saitama destroying all of the robots. When staff members of the association asked Saitama about the event, Black Sperm was hiding in Rover's stomach. Rover and Black Sperm are later entrusted to Butterfly DX, Chain'n'toad, and Forte after the latter lost a bet with Saitama after he got hit by a car. Even though the heroes protested at first, after Forte finally witnessed Saitama's true strength, he accepted responsibility for them with his compatriots and advised them to work on being accepted by Saitama as well. Forte is later seen building a dog house for Saitama's new pets.

Ninjas Arc
Rover is taken for a walk by Butterfly DX and Chain'n'Toad while his handler; Saitama, has conversations with the S Rank hero Flashy Flash. Both of whom wondering if Forte's judgement was sound or not. Rover is next seen with Genos taking it for a walk as his master heads out to settle scores with Sonic and Flash.

Supreme Hero Arc
Rover's next seen being cared for by the three A Class's when Saitama next returns with dogfood for his pet. DX admonishes Bald Cape for his poor choice of kibble for the pet and rushes out to get the right kind, with Toad asking to get a new chew toy for Rover as well. In the meantime before and after the titular heroes arrival, Black Sperm confides in Rover about whether the collective of mysterious beings was effective in destabilizing society after all. Given how the upstart hero group is undermining the veteran heroes at every turn.

Neo Heroes Uprising Arc
Rover and Black Sperm overhear about five Dragon Level threats striking at several major cities simultaneously.

Abilities and Powers
As a high-ranked member and a Dragon-level Mysterious Being of the Monster Association, Overgrown Rover is an extremely powerful being, and quite possibly one of the most powerful Dragon-level mysterious beings to date. During its battle with Garou, it effortlessly tanked several blows from him and held the advantage for the entire match. Additionally, both Gyoro Gyoro and Orochi were in shock and disbelief that Overgrown Rover was not only defeated but fled when given an order to attack Saitama, showing that defeating such a monster, even in the eyes of the leaders of the Monster Association, is extremely difficult.

Supernatural Abilities
Energy Projection: Rover is capable of firing destructive energy bursts in rapid succession from its mouth. These energy blasts are powerful enough to incinerate stone, level city blocks, and destroy several floors of the Monster Association Headquarters with ease along with severely injuring Garou and killing two Demon-level beings in a single shot. Rover's energy blasts can also cause shock waves strong enough to shake the surrounding surface area of Z-City that Saitama mistook as an earthquake. While the projectiles are presumably energy balls, Saitama noted it to be "fire".
 * Trajectory Bending: Rover can change the trajectory of its energy balls, causing them to chase after their targets.

Physical Abilities
Immense Strength: As a Dragon-level monster, Rover boasts a tremendous amount of strength and power. It was able to slam Garou against the wall and floor with ease and break Unihorn, a monster that boasted a nigh-unbreakable horn. Immense Durability: Rover is extremely tough and possibly one of the most durable monsters in the series, as it was able to withstand a punch from Saitama which shook the entire Monster Association Headquarters and left a massive crater where Saitama had struck it. The attack only left the monster unconscious for a short time, though, as pointed out by Bomb later on, the punch had noticeably weakened it. Despite this, Saitama admitted that he was going easy on Overgrown Rover.

In addition, Rover was also able to take hits from Bang, Bomb, and Garou while sustaining little to no damage whatsoever. Rover also forced Bang and Bomb to use Cross Fang Dragon Slayer Fist, a technique more powerful than even the one used against Elder Centipede and even though Rover had already been weakened by Saitama, this attack still had seemingly no effect on it.

Immense Speed: Rover is quite fast. It was able to keep up with Garou in his half-monster state and was fast enough to run horizontally across the walls of the Monster Association Headquarters. Rover was also able to keep up with S-Class level combatants such as Bang and Bomb, and was even able to catch them by surprise. Enhanced Stealth: Despite its enormous size, Rover is stealthy enough to appear behind Garou and Tareo without either of them noticing until Garou turned around. It's even skillful enough to sneak up on veteran martial practitioners like Silverfang and his brother as well as the psychic Blizzard without revealing a hint of it's presence.

Enhanced Senses: As a dog-like monster, Rover apparently has a very sharp sense of smell and hearing. It was able to detect the location of Bang, Bomb, and Fubuki when they were in hiding.

Fighting Style
Rover has no refined fighting style; its attacks are limited to bombarding its enemies with energy blasts or biting and shaking them like a dog. Whenever an enemy enters its domain with hostile intent, Rover relentlessly attacks until the target escapes or dies.

Guard Dog: Due to its canine nature, Rover is assigned to guard the entrances to the Monster Association against intruders.

Trivia

 * Rover's Japanese name "Pochi" is a common name for dogs in Japan, similar to "Rover" for the western world. Moreover, this name is similar to poochy, which refers to the disproportionate size of Overgrown Rover.
 * Murata showed Rover's design on a wedding card before the monster's manga debut.
 * In the webcomic, Garou and Rover begin to fight without encountering Unihorn, Showerhead, and Super Mouse. Garou puts a much better showing and ends up telling Rover to sit. Garou punches Rover into the ground where they were fighting, leading them to fall into the headquarters' basement.
 * Rover may be based on the Kai Ken, a Japanese hunting dog breed known for its developed muscles and agility.


 * Rover is the second mysterious being to survive a punch from Saitama, the others being Boros, Orochi, Awakened Garou, and Evil Natural Water. Though in Rover's case, Saitama was holding back and had no intention of killing it.
 * According to Butterfly DX, Rover is around 4 months old.

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