Osananajimi Succubus no Genkai Kyuuai Sakusei

A childhood friend succubus has always been by the protagonist's side, hiding her true nature and feelings. She has secretly loved him for years, but her demonic instincts are reaching their limit. Now, she can no longer hold back her desire to drain him completely, pushing the boundaries of their relationship with an all-out seduction. As her cravings intensify, she must find a way to confess her love while satisfying her insatiable thirst for his essence.