Hahahaha
(Literally, this is the only one I can think of.)
NULL NULL - Gintama dj
https://www.mangago.zone/read-manga/love_in_orbit/
he's a half human / half alien so hes got the tentacles and the human body
https://www.mangago.zone/read-manga/wave_nail/
he's not actually an octopus but he has tentacles and his dick is shaped like a tentacle
Dammit I hate that I know one. Technically he’s an octopus shaped alien thing and weirdly calls the uke “dada”. The human seme is so damn gorgeous though.
https://www.mangago.zone/read-manga/rain_advisory/
There are some interesting things in this one and it also includes a chap where the ML’s clone unleashes tentacles https://www.mangago.zone/read-manga/the_worst_guy_in_the_universe/
Also, these have side tops like that too:
https://www.mangago.zone/read-manga/tell_me_your_wish/
https://www.mangago.zone/read-manga/dark_fall/
https://www.mangago.zone/read-manga/tentacle_uo/
omg yeahhh the worst guy in the universe has so mich tentacle i forgor
Suggest me some Yaoi where the top is a octopus with tentacles