Was the uke a neko bc it might be this
http://www.mangago.me/read-manga/kiss_shite_yowamushi_kun/mf/v01/c005/2/
It could be VOID - Maki receives humanoid Arata as a birthday present. Arata is an illegal male pet type humanoid with appearance and some memories copied from stolen data of Maki's late lover Ren.
(check the line at the bottom of this page: http://www.mangago.me/read-manga/void_zariya_ranmaru/mf/a160d4b453b8d8b3e732668349b2cccc_chapter-3/pg-22/ )
Good luck!
I don't know maybe this one??? http://www.mangago.me/read-manga/koi_to_wa_yobenai/ (There's two people that have a dead lover)
Or this one http://www.mangago.me/read-manga/ikemen_kun_to_saenai_kun/ ??
Buuuuut if you know it, I'll pray for you happiness more than mine.. it's yaoi. All I remember is the uke saying 'I can't compete with that person' or somewhere along those lines. He was referring to the dead lover and he thought he's a substitute for him. I really hope somebody recognizes this