How Can I Save a Bad Ending with Quick Transmigration?

Q: How do you save a story with a BE ending?

A: Obviously, with love.

Tear your clothes off with love, power up with love. Even if I'm dead, I'll crawl out of hell to find you.

The protagonist's dad from the story next door and his CP save their BE with love.

An incredibly upbeat, sunny bottom x a relentlessly negative top who keeps self-harming.