It would be great to see which fetishes those storylines have at a glance.
We don't know which one is gay, straight, shemale, BDSM, Sissy, MtF, etc. unless we open them and read it.
Quite a lot of them are pretty clear, to be fair.
Well, there's asking Z for a free tattoo, I suppose.
But the storyline under discussion is probably one of the worst offenders in the game. The Keiko storyline is utterly opaque to the player encountering the dumb bitch faffing around inadequately with her luggage for the first time. In particular, there is no indication at all that the storyline involves NTR (which is a huge turnoff for many people). The storyline is essentially a timed minigame where the player must accumulate "relationship" points faster than Ichiro does, whilst avoiding the accumulation of "friendzone" points.
Except the only way to know this is to read the walkthrough. The player first encountering Keiko is going to have no idea that they are about to enter into a scrambling match for an unknown quantity of unknown points against an unknown adversary against an unknown clock. That, by the by, requires " charisma, intelligence, fitness and dance skills higher than average" to achieve a perfect runthrough.
What triggers this timed quest that requires such an accomplished MC? I'm so glad you asked.
Day 19. The storyline just triggers on Day 19. At which point you have to either accept or reject it.
The single biggest criticism that I can level at this game is that it is a time-management game that routinely denies the player the ability to manage their time.