Dageki Joi Saori

Ninomiya Naoto, 21 years old, gets a confession from a gorgeous woman who suddenly attacks him with a metal bat. He manages to escape, but when he`s about to die the next day he meets her again and it turns out that she`s a doctor with a "batting treatment". So she hits Nimomiya with her bat and then he`s suddenly healed. He is impressed by her method of healing so he decides to be her assistant.

(Source: Imangascans)