Leif is a rather passionate individual who will always go as far as he possibly can when it comes to new experiences. This makes him a very bold and very adventurous youth, though he's got a good amount of strength to back him up. Thanks to Aika's support, he's grown up into an adult fairly quickly. He's a lion with tan fur and deep green eyes, and has Nature Magic and Adaptability as his main powers. He also has small crystal wings, though they don't seem to do much right now. So far, he gets very excited with flirty people, and can be a bit of a playboy when it comes to flirting.
After contracting Rose Rot, Leif turned to Saga for her Love Magic for help. Saga stuck through even the worst blood expelling for his sake, and for that reason, Leif felt very grateful to Saga. After she nursed him back to health, Leif began to grow much closer to Saga to the point that he asked her to be his first Mate. When she accepted, he was beyond ecstatic, and went so far as to give her a baby girl that Saga dubbed Lovee. Leif's general attitude has become much more bright and energetic with the addition of a Love Form (Adaptability) and Saga as his Mate.
When Aika Marked him after a night of her usual gift-giving antics (including giving Crysta a Cupid's Bow), Leif returned the Mark. As this happened directly after he binded souls with Saga, this completed the Mate and Soul Bonds between the two of them as well as. Leif seems to have no problem with Aika so far.
By far, Leif is a somewhat strange individual, having a relationship with both Saga and Lovee. However, thanks to the fact that Cerian demons biology makes it impossible to receive birth defects from those within their species, the relationships are tighter knit and actually seem to be more beneficial in the long run for those involved. Though he was hesitant at first to enter a relationship with Lovee, in the end, she bowled both him and Saga over and worked hard to obtain a Soul Bond with them. She seems extremely happy now, and shows both Leif and (especially) Saga constant affection to this day.
(A work-in-progress reference of Leif.)