hee hee

they're both about trying to cure inverted nipples:

manly uke, smaller seme
http://www.mangago.zone/read-manga/go_houbi_chikubi/

older seme, younger uke (first pairing)
http://www.mangago.zone/read-manga/hitotsu_futatsu_himitsu/

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there's also this but it's a raw comic

smaller seme, older uke
https://www.nicoobook.com/p/1183450

Im sorry, this isn't a recommendation but omg when i friggen saw "sensitive nip nips" ahahaha that actually made my day, thank you. Uhh u probs already read this its not older uke or all the other criterias or criterians... idk that you requested. But i promiseee you its so freaking cute and has sensitive nips : http://www.mangago.zone/read-manga/chiku_bingo/

http://www.mangago.zone/read-manga/sokuochi_yarichin_yankee/

Younger seme- http://www.mangago.zone/read-manga/tiger_bunny_dj_old_man_s_physical_scheme/
(Bonus: seme finds out he has sensitive nipples too)