Garou is in a battle with Super Mouse, Unihorn, and Showerhead when the three unleash a combo move: Triple Demon Blasting Speed Thrust. Garou is easily able to deflect the attack, but it unintentionally strikes Overgrown Rover. While it doesn't damage the Dragon-level monster, it enrages him, causing him to destroy Unihorn.
BattleEditOvergrown Rover unleashes an energy blast. Garou immediately grabs Tareo and runs, although Super Mouse and Showerhead attempt to withstand the blast, but they are instantly vaporized. The corridor the monsters were standing in is destroyed, and Garou uses his Whirlwind Iron Cutting Fist to break through the stone.
Having no choice but to fight the monstrous canine, Garou tells Tareo to run while he holds the monster off. Tareo complains that he can't make such a trip alone, but Garou barks at the child to take care of himself for once. Running away in terror, Tareo leaves the two combatants to resume their battle. Overgrown Rover sees Tareo running and prepares to attack him, but Garou strikes his left front paw with his Water Stream Rock Smashing Fist. Garou confidently smirks at first, but his smirk fades and his face is shocked when he sees Overgrown Rover's energy blast right in front of his face. Garou knows death is close, although he got a flash back of his childhood where he was watching the "Justice Man" TV show which gave him the will power to allow his body to withstand the blast. The energy ball obliterates several floors of the headquarters.
Overgrown Rover walks to the edge of the floor and looks down to see where Garou is. The monster sees Garou seriously injured, with his clothes torn to shreds and the hero hunter coughing up blood. The Dragon-level monster fires a barrage of energy blasts, which Garou narrowly dodges. Overgrown Rover runs across the walls of the headquarters and continues to fire multiple energy attacks. Unfortunately, Garou is unable to avoid these attacks, and takes the full force of the monster's strikes. The power of these energy blasts are potent enough to destroy several buildings above ground from the tremors of his blast.
Overgrown Rover once again searches for Garou, unaware of the fact that Garou had indeed managed to avoid the blasts and is hanging from a building directly above the monstrous dog. Garou yells, "SIT!", jumps down and slams Overgrown Rover with a punch using all his strength. To the hero hunter's shock, Overgrown Rover flicks Garou off his snout and shakes his body like a dog after a bath. Garou's leg is caught by the jaws of the canine, and Overgrown Rover shakes him around, slamming him into multiple walls like a chew toy. Garou is helpless as Overgrown Rover attacks with another point-blank energy blast, which destroys several more levels of the Monster Association headquarters.
Garou is buried underneath rubble, feeling trapped but knowing that he has to get out fast in order to counterattack. However, Garou doesn't realize that he's in the personal quarters of Gyoro Gyoro, who is very impressed with his growth. At this point, Overgrown Rover decides to stop pursuing Garou to allow Gyoro Gyoro to talk to him.
Garou is significantly injured from the battle and meets with Gyoro Gyoro, who engages in conversation. Gyoro Gyoro tells Garou about his research into the concept of limiters, monsterfication, and Garou's potential to become stronger than Orochi. The psychic and the hero hunter then engage in battle while Overgrown Rover continues to roam through the Monster Association headquarters, where he eventually encounters Saitama and is defeated by him in a single punch.
- In the webcomic, the battle goes about the same, although in the webcomic, Garou is able to perform much better against Overgrown Rover, dodge more of its attacks and apparently deal more damage. Additionally, the other monsters were not present in the webcomic.