Frosted Cherry Blossoms(Sirius The Jaeger)

(Sirius the Jaeger)
Alexei never thought about leaving his tribe and the sanctuary of the village. Even as a naive child the thought of leaving the permawinter woods rarely crossed his mind. When it did, it left as soon as it came because of the questions his father instilled in him: What was out there in the human world? What good was there in a world filled with vampires? His family was here, but now Alexei is alone. And after 4 years, he's still drowning in a sea of grief with no sign of coming up for air. He didn't even want to leave his bed, much less Siberia. However, Qiuyue had different plans for him; by proposing he tag along on her trip to Japan. It was a classic adventure, nothing too groundbreaking or dangerous, it was supposed to cheer the Sirius up for 6 months. It was only supposed to affect Alexei's life for 6 months, give him some new memories and experience, then, if he pleased, he could go back to wallowing in grief. But fate had other plans and threw a being full of joy, good luck, and colorful wisdom into his life. A being that had Alexei's half year trip, seeing in pink for a lifetime.

Who was this influential being? A simple and slightly rebellious human girl, Chibana Sachiko--but she simply went by 'Sachi'.