Petting Koo is a real interaction in Beast of Reincarnation, not a background animation. The white blighted dog who travels with Emma can be stroked once you reach a specific point in the story, and doing so directly feeds his combat progression through a system the game calls Rapport.
Quick answer: After you beat Rangifer for the first time and finish the short flashback that follows, stand in front of Koo inside the Cleanse Walker, open the Talk prompt, and choose Stroke from his interaction menu.
When you unlock petting Koo
The Stroke option is locked at the start of the game. You gain access to it only after two things happen in order. First, you have to win your opening encounter with Rangifer. Right after that fight, the game plays a short flashback sequence, and completing it is what switches the interaction on.
Once both are done, you can pet Koo whenever he is with you inside the Cleanse Walker. If the option is not appearing yet, you have not cleared the flashback, so keep progressing until it finishes.
How to pet Koo inside the Cleanse Walker
Petting is one of three ways to bond with Koo. You can also shower him or give him treats, and all three raise the same Rapport value.
What Rapport does and why petting matters
Petting, showering, and treats all raise Emma’s Rapport with Koo. The higher his Rapport, the more skill slots you unlock for him, which means bonding is tied directly to how capable he becomes in combat. Koo also levels on his own track, separate from Emma, up to a cap of 100.
You can read your current Rapport Level at the top of Koo’s interaction menu, the same screen you opened to stroke him.
| Action | Effect on Rapport |
|---|---|
| Petting (Stroke) | Raises Rapport |
| Showering Koo | Raises Rapport |
| Giving Koo treats | Raises Rapport |
| Letting Koo fall in battle | Lowers Rapport Level (never below the current rank) |
Note: If Koo goes down during a fight, your Rapport Level drops, but it will not sink below the rank it has already reached. Progress toward the next rank is what you lose, not the ranks you have already earned.
Item and Skill Research in the same menu
Koo’s interaction menu is also where you assign his Item Research and Skill Research. It is worth checking these regularly so you are not sitting on an unclaimed skill or item that Koo could be working toward.
If no Item Research is available to assign, that usually means Koo has nothing new to study. Head back out into the world and look for a book holding lost knowledge, which gives him fresh research to take on. Between the bonding actions and the research slots, keeping Koo in good standing pays off every time you head into a Nushi fight.
