Episode: Shingetsutan Tsukihime - 8 - Origami b432h

When Shiki returns home, Akiha collapses shortly after a conversation with him. Kohaku claims she will be fine, and Shiki stays with her through the night. The next day, he is strangely asked by Ciel to allow things to stay normal longer. At home, he sees Akiha taking blood from Kohaku's breast. Arcueid later reveals that Roa reincarnates in the bodies of families with inhuman characteristics, leading Shiki to believe that Akiha is Roa. Later that evening, Shiki follows Akiha, watching her hair turn red. Shiki then goes with Arcueid, but after leaving her, he is attacked by a man who can see the same lines as him, and Shiki is cut across the chest. After Ciel forces the man to retreat, Shiki collapses.

Source: theTVDB.com