Rin has always been rough on Isagi, he thought Rin might change during sex but nothing changed. He never asked Isagi if he wanted this if he felt good or if he needs prep; he just does it and leaves Isagi all alone like always. It's nothing new, because they're just rivals with benefits. But they can't help but catch feelings. (Hey guys! First time writing Rinsagi. Warning: Mature themes, angst. The beginning will be rough but the ending is happy one, don't like don't read, if you're under 18 I suggest not reading it as it contains smut.)