Keita Tachiyama

Keita has been friends with Rina since they were small and always tried to protect her whenever people are messing with her in a perverted way when they're young (although he secretly peeks her panties as well when he's defending her). Keita joins the love triangle in this manga because Rina never take his love seriously and he didn't give his love up for Rina even though she then had a boyfriend until the end.