It's a combo if Ike confessing and the end of volume 14.
Shana + Kazumi send letters, Ike runs into Kazumi, he confesses, she rejects thinking Yuuji picks her, he then disappears. He disappears and no one notices right away.
Yuuji is thinking about what happens if another Sabrac appears, Snake speaks up, they talk, Yuuji breaks free from the world's stage by becoming a Tomogara.
Kazumi and Shana wait long into the night.
Yes, next week is very baaaaaaaaaaaw inducing. But 23 and 24 should make up for it with "holy shit - FUCKING GAR!"