On his debut tournament (basho) in July 2012 he won all seven of his regular matches in the jonokuchi division but lost the championship in a play-off against his stablemate Iwasaki.

[1] On Hamaguchi's debut in the fourth sandanme division in November 2012 he won four of his seven bouts to record a winning score or kachi-koshi.

In the following tournament in January he was undefeated in seven matches to win the divisional championship (yusho) and secure promotion to the third, makushita level.

He quickly established himself in the upper ranks of the division and in January 2016 he was narrowly denied a yusho when he was beaten in a play-off by his stablemate Ura.

Competing towards the top of the third division for the rest of 2016 and throughout 2017 he performed consistently before a 5–2 result in January 2018 secured his second promotion to juryo.

In the second week of the basho he showed considerable improvement and won his last six bouts including wins over Yoshikaze, Kotoeko and Takarafuji.

He then found life in makuuchi more difficult, recording only one kachi-koshi in the next six tournaments, and he had fallen to the very bottom of the division at maegashira 17 by November 2020.

[5] Shimanoumi has shown a preference for tsuki and oshi techniques which involve pushing and thrusting rather than grasping his opponent's mawashi or belt.

[6] In December 2021 Shimanoumi announced his engagement to Sayaka Fukuzono, a former Takarazuka Revue singer who performed under the name of Chihana Amasaki [ja] and the eldest daughter of the late former sekiwake (and former head of the Izutsu stable) Sakahoko.