Did bro unintentionally groomed her?
Naw, you can't unintentionally groom someone, that's not how grooming works. The guy was just an above and beyond good dude. Despite Japan's rigid hierarchical societal norms, he used Keigo(polite speech usually reserved for peers and superiors) when talking to a high school student who was also a woman, then he continued to come to the grandma's house only to play with the dog, expecting nothing of the High school girl, and finally when the dog died, he brought her a consolation bouquet arranged such that every flower reminded her of the dog she had lost. That's Rentaro levels of kindness and consideration, and if that dude can bag 100 girlfriends (as well as the majority of the readers regardless of gender), this dude can impress one.
