is there any way to do the nanako handjob later in the story if i skipped it in the intro?
Viewing post in Club Detention v0.0861 comments
If you're on version 0.0873, galleries have been added so you can replay the scene again. If you didn't encounter the HJ though, you'll have to look for an old savefile and select the options differently.
Edit: I think I understand your question better. If you save your current point, you can restart the game and speedrun to Nanako or open a savefile that was closest to it. Finish the scene. You can now go back to your current point and if you're on the latest version, it will unlock in the gallery. It does not have to be the same gameplay, it just needs to be unlocked once and any gameplay will be able to see it in the gallery now.