けっぱん· also けつばん、ちばん
seal of blood; sealing with one's blood
Noun, Suru verb
しかもメモの下側したがわにあるのは汚よごれじゃなく・・・け、血判けっぱん！？
Moreover, what's on the bottom of the memo isn't dirt but a ... b-blood seal!?