Regardless of the outcome of the first challenge with,... Akari? Whatever his name is. As long as you're not significantly transformed/brainwashed just prioritize buttering it up with cinnamon-roll snek. On the third chat about hypnosis, (the one after telling you about "the family business" as it were and asking your opinion) be marked as vulnerable when you hit him up and he'll change you. Any pairing of genders works! Also takes all your influence so be sure to spend it! Fastest way to speedrun it is to also pal up Rhianna or Marazet in the first mingle phase and lose the second challenge (chess game, the other two are conniving little bastards!) and you can finish it off in the second phase.
Not quite! There's a female variant if Lewis has already been TG'd by someone else. But that'll take some trial and error, as a lot of transformations will conflict and quite a few are outright incompatible/lock you out of any other route than the they put you into (Matthias being one notable example.) But yeh! Fish Lewis is precious!