You need to go peek Charlos room after he take Yamato.
There 2 scenes in different days where you peek at them. The last one is a bit before this version ends and also the one you asked. You can see the scene on your folder in video i think.
This dev while is making a interesting game he should give more hints for what people need to do next. Several times you read what they said (aka the hint) and you arent really sure what to do next. So your solution is check every thing but first going to where the next scene is. Like he call Yamato to go to his room and you go there and find a heart symbol which means some hentai event is going on there.