@tungwhatup: If the so in maso (and, by proxy, "source of mana") is what I think it is (that is, 素), then the translation should be "element" rather than "source", given the context in page 11.
Demons should be good at offering deals to willing customers, so he did manage that much. Though a demon's deal should always have a catch. I wonder if he figured that detail out yet.
No no, the loli girl transformation was clearly calculated. By appearing as an attractive member of the opposite sex, she gets tons of additional perks for free.
she can guard you. to be fair that is quite a win considering the issue with being weak first and needing to progress and grow into an actually fearful demon.