Will accidentally draw her first sexual experience into a manga... that they will show to everyone... and not realize what they did until it's too late.
When under time pressure, easiest to just use what you know aka things that happened to you. Plenty of reference material from this summer... from when they lived alone together for a week... and so much more...
I'm sure you have a lot of experience with love now Yuu, but you'd better get that project done immediately! You don't want to spend less time with Keita, after all!
Will accidentally draw her first sexual experience into a manga... that they will show to everyone... and not realize what they did until it's too late.