Responses
http://www.mangago.me/read-manga/iberiko_buta_to_koi_to_tsubaki/
the uke of the second couple in this manga have this feelings. the story about the second couple starts in the last chapters of the first volume if I remember correctly.
http://www.mangago.me/read-manga/lover_s_position/
(also some other Minase Masara's oneshots)
Hello! Do you know a manga where the uke or seme feel like they are substitute of someone though they are not. Like they feel that the other one is better for their lover or in any other way feel that they are not good enough. Thanx!