MODS
Sequel: Gary's story http://www.mangago.me/read-manga/nights_before_night/
Souyuu Ganbou no Hanashi
Sequel: http://www.mangago.me/read-manga/koyu_ganbou_no_hanashi/
Young Bad Education
It has age gap but the stroy is soo amazing, too good for words. Very wholesome and makes you feel good. Specially the sequel is just too wholesome and a great reading experience. Couple growing old together and have happy life ️ Sequel (must read story, love it!) https://www.mangago.me/read-manga/young_good_boyfriend/
Back to School
Sequel/ Spinoff/ time skip story: https://www.mangago.me/read-manga/back_to_school_all_grown_up/
Tadoru Yubi
Spinoff/ sequel: https://www.mangago.me/read-manga/torokeru_kuchibiru/
Sahara no Kuro Washi