Red strings (Giyushino week Day 1special!)

In this AU, everyone is born with a thin red thread tied around one finger, invisible except under certain circumstances. It connects them to the person they're destined to love.
Except Giyu has never been able to see his.
Naturally, he assumes that means he simply doesn't have one.
Shinobu absolutely torments him over this. But during a mission, Shinobu is badly injured and Giyu catches her hand to stop her from falling.
For the first time, he sees it.
A tiny red thread wound around his finger.
Running directly to hers.
And Shinobu sees it too
still she has her plans involving Dōma and Giyu still thinks he's undeserving of happiness. So instead of instant romance, knowing they're supposedly destined for each other makes everything more painful.
Because eventually Giyu realizes:
Shinobu is planning to cut the thread herself.