1) High School ☆ Lullaby [Gesu BL]. - The Uke suddenly ties the asleep Seme & raped him http://www.mangago.me/read-manga/high_school_lullaby/
2) Shoujo C [Joshi BL] - Their gal classmate sees them & Koizumi's true indentity http://www.mangago.me/read-manga/shoujo_c/
3) Requirements for Being Trash [Kuzu BL] - Back story of Koizumi since he was a child. http://www.mangago.me/read-manga/kuzu/nbt/tr_chapter-3/pg-1/
4) Don't Take Off Your Gym Uniform - Their changed relationship after they had sex. http://www.mangago.me/read-manga/gakuen_tengoku_sore_wa_koi_desu_koizumi_kun/nmt/c001/1/
5) Lonesome Neon Tetra - W/o realizing Kashihara’s jealous! Meanwhile Koizume thinks about making their feeling mutual. http://www.mangago.me/read-manga/gakuen_tengoku_sore_wa_koi_desu_koizumi_kun/nmt/c002/1/
This is a continuince of a story that started in other mangas. 1) Kuzu 2) High School ☆ Lullaby (http://www.mangago.me/read-manga/high_school_lullaby/) 3) Shoujo C (http://www.mangago.me/read-manga/shoujo_c/)
Related Series: 1) High School ☆ Lullaby (Gesu BL) >> Backstory for Koizumi: Requirements for Being Trash (Kuzu Anthology) 2) Shoujo C (Joshi BL // Sequel to High School ☆ Lullaby) 3) Taisoufuku o Nugasanaide (Sequel to High School ☆ Lullaby)
http://www.mangago.me/read-manga/gakuen_tengoku_sore_wa_koi_desu_koizumi_kun/