Under the Skin (KUSABI Keri)
Uhm I think the butler really had an unrequited love for the late master...but then, after his death, all the things he did were for young master's sake only. And he did so much for him, indeed. But the young master, Rui, didn't realize it...he thought it was just because he was the late master's son. At the last page he finally understood: "You...how many guys have you told those words to up until now?" Also, Kuroe said before: "Why does my voice never reach him? Everytime I try to convey it..."
Oh, My Young Master!
Kimi wa Pochi Da! ~Daigakuseihen~
Apart from the fact that it's dropped, there's also a prequel to this story that isn't scanlated: https://www.mangaupdates.com/series.html?id=25430
Hachimitsu Ouji Wa Shitsuji Ni Madou
Goshujin-sama to Kemonomimi no Shoujo Meru
Shitsuji-tachi No Chinmoku (sakurada Hina)
Age Gap, Older Male, Butler, Master x Servant The guy is HOT and I really like the art.
Hatsukoi ni Kisu