Injuu Alien

Both are criminally underrated pre-2000 sci-fi horror anime. In both mysterious things happen onboard a space craft with a lot of murders as a hidden threat takes out the crew one by one. Injuu Alien is a pinku (story-based hentai), lots of tentacle rape. Lily C.A.T. is far less explicit. Both anime have very similar plots and stories, and the same sense of old-school sci-fi horror. They're both from different generations, Injuu Alien from the 90s and Roots Search from the 80s. Lily C.A.T. is more slow and steady, whereas Injuu Alien is more fast-paced, but if you liked one (and are open to hentai) then check out the other. read more 

Both are criminally underrated pre-2000 sci-fi horror anime. In both mysterious things happen onboard a space craft with a lot of murders as a hidden threat takes out the crew one by one. Injuu Alien is a pinku (story-based hentai), lots of tentacle rape. Roots Search is a relatively less explicit (but still absolutely not for children). Both anime have very similar plots and stories, and the same sense of old-school sci-fi horror. They're both from different generations, Injuu Alien from the 90s and Roots Search from the 80s, but they close the generational gap in how similar they feel. 

Both anime are set in a futuristic sci-fi universe with spaceships and female protagonists. The other similarity is the rampant tentacle monsters which are violating the girls. What a terrible monsters they are! 

Both are horror, monster/tentacle hentais containing a little gore. They both have similar looking scenery, a similar story and ending.