Tsukiyama Shuu x Reader - Diminuendo

Diminuendo - The musical term to decrease in volume, to diminish.

You'd thought your relationship with him was perfectly fine, but he'd suddenly changed and spent less and less time with you.
Eventually, you were completely cut off from his life, yet still held the position of 'Tsukiyama Shuu's Girlfriend'.
And as your final decision in response to his, you'd decided to 1000%, completely and permanently, cut off your life from his as well.