in my vision the story will be more fast-paced / using time skip; because we need chiaki to be semi professional here.
one day chiaki and ai got photographed in public. so they have to pretend that chiaki is a new designer that will collab with ai, but ai's manager/team come up with a challenge that chiaki has to make more professional works (or making name for himself a bit) first. so chiaki somehow has to work with that model (mizuki). anyway after they got close after a lot of frictions, chiaki introduced punk to mizuki and mizuki began to like punk. (punk is important theme of this story why there's barely any punk in this volume).
anyway chiaki and mizuki will have good chemistry, chiaki will feel a bit like ai who taught old chiaki new stuff, this time chiaki is the teacher to mizuki (about punk though). ai will be terribly jealous but it's suit the name punk triangle, there has to be pseudo triangle here. I mean ai is jealous but we readers can see that mizuki is bottom material lol and they're just two besties. miki can show up as mizuki's love interest, miki will be already a professional designer and not in the same night school as chiaki (i think author using the design school as center is limiting the story potential).
anyway there can be nice side quest/mini arc with miki and mizuki without sidelining ai and chiaki. so the story can become a long series....
overall in my vision, ai will not be as much plot-relevant except becoming chiaki's major morivator ah and provide fan service sometimes. imho since chiaki is already a good protagonist it's good enough to focus on him. there will be still ai crumbs as model, i really think ai is too hot and too precious to be in every panel. so, making scarcity out of him will be more exciting. and you know, make up a new distance to make him hotter.... although reader already see his clumsy side as enaga, it will still works to give back some mysterious aura and unreachable aura back to ai... then as motivation ai ask chiaki to go to a date and they can reminisce about the past while also having another episode of partying at night... good enough fan service.
I feel this setup can works for a 3rd volume, is it deliberate??
ok now review
the friendship is nice. Chiaki grow up so much
but the double jealousy and misunderstanding ain't cool. I know japanese love that kind of theme but I never understand why
overall it has very different feeling from volume 1. I think volume 1 is so effortlessly hot and whole it's hard to replicate. basically chiaki and ai's story ended there.
i think volume 2 should be a spin off instead with chiaki and ai as the side characters, or inspiring couple. anyway that's what i get.
if they still want to make chiaki x ai story, I think it'll be interesting to explore more on the professional's side. for example chiaki still hasn't accomplished his designer dream. chiaki worked hard to be a named desginer while ai has been more busy. ai has no progress on the school and bc he's busy he has to stop going there but he secretly practice by himself. they still met secretly and done the deed in public bathroom like in this volume. then chiaki has to work with another model possibly that man who seem to dislike ai. i think if misunderstanding happen there it will be more natural bc the new guy directly replace ai as model while working closely with chiaki. i think his personality is like the old chiaki who was prickly it will be fun to see them become friends after they worked hard together... i ended up writing a fanfic