>>11303866
>The succubus came off like an evil manipulator for the whole run and in the end she apparently could've regained a humanoid form at any time without actually needing Ayamu to turn into a girl or blow hundreds of dudes

I think the relationship was that one-sided. Lyna did seem to care for Ayumu. She did try to warn Ayumu that if she used too much power (Lyna literally had a gun pointed at her at the time), she would become a succubus like her >>11302832. An evil manipulator wouldn't have given a fuck and told Ayumu to do whatever it takes even if it meant the lost of her humanity. Also, Lyna's transformation back to a succubus wasn't until the very end and even then she was "underdeveloped". IOW: Lyna didn't have the ability to transform back until Ayumu blew hundreds of guys (and giving the energy to Lyna).

>>11304845
>He grew to enjoy it I think

That happened after Ayumu got perma-girled. Pic is from chapter 8. In the previous chapter, Ayumu turned into a girl without Lyna transforming her. This is the turning point in the story where Ayumu stayed a girl.