Houkago wa Kenka Saikyou no Gal ni Tsurekomareru Seikatsu Kanojotachi ni Sukarete

Shiki, an honor student at a bottom-feeding delinquent high school, has a crush on Karin, a beautiful gal who also happens to be the strongest fighter in school. When Shiki steps up to help her against a gang of delinquents, she falls in love with him, too. While Shiki tries to teach Fumiki to study, she teaches him how to fight...... (but she keeps getting flustered when they touch)

Karin's gal pals also like Shiki and try to get friendly with him. They fondle him, give him sex tips, and...... While being teased by the gals, Fumiki gains the strength to defeat any delinquent, and his reputation around schoolchanges drastically!

(Source: Fantasia Bunko, translated)