So I've good ended 10 girls so far and based on my playthroughs the trainers are:

>Oguri Cap - Blank slate
>Silence Suzuka - Blank slate
>Tokai Teio - Blank slate
>McQueen - Blank slate
>Special Week - Blank slate
>Daiwa Scarlet - Not!Boyfriend
>Rice Shower - Oniichan
>Haru Urara - Wish foundation worker
>Taiki Shuttle - Blank slate
>Sakura Bakushin - Sociopathic manipulator
>Grass Shower - Servant to a Samurai
>Agnes Tachyon - Loyal assistant
>King Halo - First-Rate Partner in Crime

I'm sensing a pattern that the more stars an uma has, the less relevant the trainer is to their story. Rice Shower's kinda an exception but she is just such a shit to train up. The King Halo scenario is miles ahead of any of the 3 starers and actually put me as a reader where the trainer is at key points head-wise. Would totally vote for her and let her steal my jacket.