Unubold accepted an invitation to come to Japan to enter sumo and while still a teenager he joined said Shikoroyama stable, taking the ring name (shikona) Seirō, meaning "blue wolf".

[1] Seirō made his debut as a 17-year-old in September 2005 when he won five of his seven bouts in the lowest jonokuchi division and was immediately promoted to jonidan.

In the first three tournaments of 2015, Seirō made kachi-koshi, recording nine wins in January, eight in March and eight in May to earn him promotion to the makuuchi division.

[1][2] On his makuuchi debut Seirō won seven of his first thirteen bouts but lost to Yoshikaze and Homarefuji on the last two days to end with a losing record (make-koshi) of 7–8, which nevertheless enabled him to maintain his place in the top division.

He again recorded a 7–8 result in September – although he won seven of his twelve matches against makuuchi opposition he lost all three of his contests against jūryō wrestlers.

In March he was more consistent, recording a 9–6 score including a top-division win over Satoyama on the final day to all but ensure his promotion back to makuuchi.

An 8–7 record in July kept him in contention for promotion but a disappointing performance in September saw him drop to the lower reaches of the second division.

Sanshō key: F=Fighting spirit; O=Outstanding performance; T=Technique     Also shown: ★=Kinboshi; P=Playoff(s) Divisions: Makuuchi — Jūryō — Makushita — Sandanme — Jonidan — Jonokuchi