Kairyuu to Yuubinyasan

Hana, a girl from the Paldea region, dreams of becoming an ace mail carrier like the Dragonite postman she admires. When she finds a letter with no destination, she refuses to let it disappear into the system and sets out with her partner Fuecoco to find whoever wrote it.

The search leads them to a boy named Rio, who wrote the letter for his father working far away in Kanto as a birthday message. But the birthday has already arrived, leaving no time for ordinary delivery. Hana, Rio, and Dragonite race against the distance, because one simple letter may be the most important package they deliver all day.