Talk:Monster Musume: Everyday Life with Monster Girls (anime)/@comment-73.168.18.226-20150810214448/@comment-26824352-20150902165100

It would appear to be a case of the latter, to keep in line with the manga.

Lala does not exhibit romantic inclinaton toward Kimihoto (or anyone, really). Though it could be argued that she is still attracted to him, it appears to come down to  peculiar instance of "you'll be mine forever when you die, I can wait that long" revealed in the chapter with all thenear-death experiences when Kimihoto talks to her on the flowery plain of what I suppose is his unconsciousness or something.

Indeed, her appearance even after she's in the house is spotty. This is not an accident: she's meant to have a dismisable presence. She's not there for romance, she's there to keep him from croaking. In this manner, it makes sense that she wouldn't be one of the six participating in the opening, although you would think she'd show up briefly in the same manner Smith and the MON team does.

Of course, it's worth remembering Lala could technically be a walking spoiler in that context. The letter from D and its mystery would be undone if she appeared in the opening unless she was also alongside Draco, Lilith, and Kii, and those three are too tertiary to be featured there and are also minor one-episode spoilers of their own.