Lumine bursts in to find Tartaglia finishing inside Skirk for the seventh time. Her fury locks onto the smirking mentor instead of her unrepentant boyfriend.

Skirk panics, spilling the truth: Lumine’s outer-worlder body devours Tartaglia’s power mid-act, draining him before he can satisfy her properly. That’s why he’s been “recharging” across Teyvat.

Lumine calms... slightly. But manhandling her boyfriend? Unforgivable.
Now Skirk’s the one getting punished—by a vengeful girlfriend and her suddenly very motivated student, using this opportunity to satisfy her since a very long time.