
As a comment below said, in chapter 109, it may be Real Ciel the Undertaker is talking to.
And if I remember correctly, the Undertaker is a former shinigami ..
what if he was the one in charge of recovering the souls of the phantomhive at that time and decided it was unfair or something for Real Ciel (and/or the whole family), took pity on him which made him quit being a shinigami and start searching for a way to bring back Real Ciel for whatever reason ?
Hmm ..

wait I feel very stupid right now ..
The warlock, what’s his goal in all that mess ? Is it some kind of revenge ? I’m lost (._. ;)

Escape before it's revealed he's a warlock (witch) and figure out what he should do in life.
He knows he can't return to the witches, so he'll need to go somewhere else... Obv so Ryan can find him later.

I don’t know why I’m thinking about that but in most mangas, characters are usually sleeping on their back. I mean I know it usually helps the scenario, but I always felt weird sleeping in this position, somehow I feel very vulnerable so I sleep in a fetal position... I’m curious: are there a lot of people who sleep on their back ?
Anyway why am I talking about that here, sorry .. ._.
Anyways, it was extremely cute. Kotarou was the definition of cuteness ╥﹏╥

Well japanese culture is very centered around living a long healthy life, one of the reasons they have good posture and stretch so much and stuff. Laying on your back is technically the healthiest way to sleep (other positions cause joint pain and tight muscles) so if this goes along with their pattern of ingraining healthy living since birth, it doesn't surprise me that many japanese sleep in this position
Never cried so hard reading a manga except for Hana to Ryuu..
It’s gonna take hours before I stop thinking about it and crying┗( T﹏T )┛