Sorry Furuhashi, you want some Nariyuki loving without hurting your friends? I got two words for you.
Harem
Plan
Talk to Momo, she'll explain it to you.
One moment you're an honor student, working diligently to get into the best university you can. Next moment you're tied up like a Christmas ham getting your fundamental orafaces plugged by random J pornstar while moaning like a chipmunk in a blender for your onii-san.