I really am hopeless at writing. I have no patience or anything.
Since A Yin transmigrated too, shouldn't Multi-Transmigration Guy get to transmigrate once as well?
So, Multi-Transmigration Guy, become Sasuke.
Make the Uchiha clan's giant chuunibyou jar even darker.
The setup is that Multi-Transmigration Guy and A Yin argue, then he drinks alone to drown his sorrows and somehow transmigrates.
He discovers he's become Sasuke.
After countless hardships (not really), he reunites with A Yin.
And then...
HAPPY ENDING