@hupopi Judging by the outfits, they're in their Kai Ni forms. Based on the game CG, they are definitely more mature looking, imo bordering on fully mature. Some artistic license going on here too, but I don't mind it.
Also, another great Asa/Arashio doujinshi! Agree with notthisagain that more of Arashio's pantyhose is needed, in all of its glorious tightness.