Wild conjecture time, which absolutely should be entertained. Is it feasible that demon Mika shows some familiarity with Yu and their family, and has the same inner fears because he picked up on them since he is a part of Mika in the same way that Shikama Doji can pick up on Shinoa and Mahiru's experiences.
This is continuing the possible route that Mika and Mikaela are separate entities, Mikaela the demon doesn't seem a forgetful 'pure' demon so to speak who's regarding his emotions manifested in the form of Mika (like humans demons would experience memories themselves, rather than from the perspective with themselves as a third party, unless that's something new introduced), he still has the capacity to form his own feelings, and memories are able to be retained. Where the plot of chapter 104 is concerned perhaps it was misleading readers into assuming Mikaela breached Yu's heart and became the teenage human appearing Mika since it was on the next page and part of the story so is the obvious inferance.
Recollection scenes are increasing, maybe there would be one later which shows Shikama Doji finding Mika in the dream world house and that's the Mika who is searching for details on Yu where he finds that large eye, on a particularly large aim in the dark theory/prediction.