Luna Ishikawa, a vampire transfer student, cultivates an image of cool mystery and poise that earns her school popularity. This facade masks a critical flaw: she cannot properly suck blood, causing profound distress and embarrassment that clashes with her perceived elegance. To manage her resulting hunger, she substitutes sweets for sustenance.

Her hidden vulnerability emerges when classmate Tatsuta Ōtori accidentally uncovers her secret during cleaning duty. This exposure shatters barriers, revealing her true clumsy, timid nature instead of aloofness. Tatsuta offers a solution: his blood for practice in exchange for her training him, establishing the basis for their evolving dynamic.

Guided by Tatsuta and through repeated practice, Luna incrementally hones her skills, each attempt advancing her progress. Concurrently, she develops romantic feelings for him, layering emotional complexity onto their relationship. Her journey focuses on reconciling her public persona with private insecurities while mastering this fundamental vampiric ability.