I like to base my plots off of songs, so here's a litter. I advise you to listen to each song to see if it gives you muse lmao. 
There's two sections, and non . can probably be added or taken away from any plots tbh. I like angst a lot, and fluff. Mhm oh yes, let's find the perfect combination.

Non Plots:

FourFiveSeconds - Yuji is having an existential crisis of the sort, and in a work/idolship-related breakdown, she calls you and asks if you want to go on a spontaneous roadtrip. Filled with late night bonfires, crazy borderline-illegal activities, and the occasional heated quarrel that turn into you two bundling up in the back of your car. 

One Dance - She's always been someone you've looked up to, whether it be because you found her talented or attractive---and when you find yourself fidgeting helplessly while asking her to dance at an idol party, you guys end up having a blast. Getting complacently drunk, you both find great friends that night

Paper Hearts - You've just gotten out of a devastating breakup, and Yuji was the one to help you out of it. She was the one to always help you out of it, while making happy memories to replace the painful ones. Includes lots of cuddling/skinship, trips to carnivals and basically just lots of fluff from Yuji. 

Just Hold On, We're Going Home - (Possible trigger warning) - In a crying heap, Yuji calls you up stating she's just been ually assaulted at a bar, and that the men were still following her, and she needed to be picked up. You launch out of your bed and go to meet her, where you get into a physical altercation with one of the men, before wrapping up a ruffled Yuji up in your jacket and taking her home where you spend what time you can making her feel better, making her feel safe again.

Plots:

Needed Me - Yuji's known to be independent, and so are you to an extent. At a behind the scenes party, you two hit it off and have a wild one night stand that leaves Yuji stumbling out your door in the early morning. She left behind however not only a piece of her undergarments, but a sense of emptiness she managed to fill that night, that you never even realized you had. Now together you two struggle with building a friendship around feelings you are not even sure of, feelings you doubt she'd ever return.

Own It - You've been ing around with Yuji for a while now behind the scenes, and when you guys are almost caught during an escapade right before your group's stage, she admits that she'd like to explore something more with you other than . Includes angst and an explicit rendevous in a music show's innards right before a stage, because you considered it to be your "good luck ."

Back To Sleep - You and Yuji are the best of friends in the idol world, and after you've spent awhile overseas, you lost contact. Since then, she's become inherently grumpy at your lack of communication, so when its your return date and home celebration, she doesn't show up. Begrudgingly at first, you sneak into her dorm and crawl into bed behind her, being the big spoon you always loved to be, as an apology because if it was one way to make her melt, it was like this. After a heated conversation, the friendly skinship turns into something more.

Gangsta - You and Yuji are paired together for a dance collaboration, using the song "Gangsta," by Kehlani. The choreography was explicit before you guys toned it down, but while practicing the latter, "steamier" choreo-----let's just say some goes down in the practice room.