Jishou wa Kyuuketsuki-chan Kaiitan

Luminita, a self-proclaimed vampire, comes to Japan to fulfill the request of her late friend. Her friend was a collector of supernatural events, and his wish was for Luminita and his son to complete an unfinished supernatural story. However, his son, Yutaka, doesn't believe in supernatural events at all. Although she is captivated by the gentlemanly Yutaka, Luminita tries to fulfill his friend's wish...

(Source: Natalie, translated)