"That's right, Shu. We promised, didn't we? That day, we said we'd always be best friends..."
Tsukuru lives with Shu, his childhood friend whom he's secretly in love with. But because they're "just friends," he knows he can't hope for anything more. To cope, Tsukuru starts sleeping with someone else. His new partner, Kusumi, proposes a condition during their sex play: to use handcuffs and a blindfold. But one day, in the middle of their play, Tsukuru accidentally bites Kusumi's finger...
