Overgrown Rover

Overgrown Rover (育ちすぎたポチ, Sodachisugita Pochi), or Rover for short, is a Dragon-level Mysterious Being and an executive member of the Monster Association. Its role is to guard the Monster Association headquarters from intrusions and danger.

'''The following section contains Webcomic spoilers. You have been warned, manga-only readers.''' After the Monster Associations downfall, he became Saitama's pet alongside Black Sperm and is currently entrusted with Forte, Chain'n'toad and Butterfly DX.

Appearance
Rover is a very large black six-eyed dog like creature. Its eyes are ruby colored. It has very large fangs and four toes for each paw. Its fur is very roughed up. It seemingly lacks a tongue.

'''The following section contains Webcomic spoilers. You have been warned, manga-only readers.''' After the battle between the Hero Association, the Monster Association, and Garou, Rover was speculated by Black Sperm to have been weakened since it has gotten smaller in size.

Personality
Rover behaves like a dog. It is a diligent and loyal guard dog, instantly tracking down Garou after the Hero Hunter helped Tareo escape and did not stop 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 he neither attacked nor followed Garou and Tareo in his initial encounter with the pair, leaving them alone when they backed off slowly. Additionally, Rover does not seem to differentiate from friend or foe when angered, as he attacked and killed fellow monster Unihorn after the latter accidentally hit Rover during a fight with Garou. Rover also is afraid of beings stronger than him as he ran off from Saitama, disobeying a direct order from Orochi, because Saitama defeated him earlier.

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

After Garou and Tareo slowly walk away from Overgrown Rover, three other Demon level monsters, Super Mouse, Showerhead and Unihorn appear and fight Garou. Unihorn uses his Trinity Demon Bursting Speed Thrust and launches itself at Garou. Garou brushes him off, and he shoots into the distance. Garou takes a moment to realize that that was where Overgrown Rover was, and hears its roar. Unihorn's head is then thrown back all broken up. After a moment, Rover finally joins in the battle and fires an energy blast from his mouth. Garou grabs Tareo and narrowly outruns the energy blast. Once Garou makes it to the surface, he tells Tareo to run while he handles Rover. Garou strikes Rover's front left leg in an attempt to throw him off balance, but Rover merely shrugs it off and fires another energy blast. This time, Garou is unable to escape it, and is forced to take the full brunt of the blast, which destroys several floors of the Monster Association headquarters in the process. When Rover sees Garou standing, he fires a rapid barrage of energy blasts as he runs across the walls. This time, Garou manages to avoid all of the attacks, and strikes a powerful blow on Rover's forehead.However, Rover merely shakes off the attack and comes out completely unharmed, shocking Garou. Rover then bites down on Garou's leg, and shakes him around like a rag doll before shooting another point blank energy blast at Garou, which destroys several more floors of the headquarters. Afterwards, Rover stops pursuing Garou and allows Psykos to finish Garou off. While Saitama is roaming the Monster Association headquarters, Rover encounters Saitama. Rover growls angrily at Saitama, then fires an energy beam at him. Saitama jumps over the beam, calling Rover a "bad dog" and remarking at his lack of training. Saitama tells Rover to sit and punches Rover into submission.

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, but upon seeing him, he recognizes him 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 Overgown Rover a beating, and the two resume their battle.

'''The following section contains Webcomic spoilers. You have been warned, manga-only readers.'''

Afterwards, Rover encounters Fubuki, Genos, Bang, and Bomb, who were trying to enter into the headquarters. Rover starts fighting against them and during the battle none of the members of the group are able to injure Rover, even after using their combined attacks. Out of annoyance, Bang rhetorically asks why Rover couldn't simply be quiet and sit down. Rover, remembering being forced into submission by Garou and Saitama after they gave the same command, obediently sat and stopped the fighting. For the remainder of the invasion, Rover's enormous size began to reduce drastically until it became no bigger than an average dog.

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 decided to follow Saitama as well, thinking that his chances to survive were bigger with him, and together, he and Rover persuaded Saitama to take them to the Hero Association's headquarters in A-City, which the hero only begrudgingly accepted. At the entrance however, the secuity system recognized Rover and Black Sperms as monsters and sent defensive robots to deal with them. Black Sperm was hiding behind Rover, who was growling at the robots and they then witnessed Saitama destroying all of the robots. When staff members of the association asked Saitama about the event, Black Sperm was hiding in Rovers 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 over them with his compatriots and advised them to work on being accepted by Saitama as well. Forte was later seen building a dog house for Saitama's new pets.

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 his battle with Garou, he 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 his 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".

Physical Abilities
Immense Strength: As a Dragon-level monster, Rover boasts a tremendous amount of strength and power. He was able to slam Garou against the wall and floor with ease, and break a monster that boasted possessing a nigh-unbreakable horn.

Immense Durability: Rover is incredibly durable, being able to withstand hits from Bang, Bomb, Garou, and even Saitama without receiving any or little damage, a very impressive if not nearly impossible feat to accomplish, although Saitama admitted he was going easy on Overgrown Rover. Rover also forced Bang and Bomb to use Cross Fang Dragon Slayer Fist, a technique more powerful than the one used on Elder Centipede.

Immense Speed: Rover is quite fast and able to keep up with S-Class heroes such as Bang and Genos. He was also able to outpace Garou, and was fast enough to run horizontally across the wall of the Monster Association Headquarters.

Enhanced Stealth: Despite his enormous size, Rover is stealthy enough to appear behind Garou and Tareo without either of them noticing until Garou turned around.

Fighting Style
Guard Dog: Due to the canine nature of Rover, he is assigned to guard the entrances of the Monster Association against intruders despite being a Dragon-level monster and an executive of the association. Whenever one enters his domain with hostility, Rover immediately and relentlessly attacks them to the extent of completely destroying them, seemingly giving up only when the target is dead or escapes. Despite appearing to have no teeth, Rover can easily bite down on opponents and shake them to snap their bones.

Trivia
'''The following section contains Webcomic spoilers. You have been warned, manga-only readers.'''
 * Rover is the second mysterious being who has survived a punch from Saitama, the other 3 being Boros, Awakened Garou, and Evil Natural Water. Though in Rover's case, Saitama was holding back and had no intention of killing him.


 * Murata has shown 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 headquarter's basement.