In his childhood, Sugano had no interest at all in football, as all his friends did, and didn't even bother to watch games on TV. He was more interested in grappling sports, such as judo, which he practiced for a time. When he was sixteen a friend of his father's suggested that his already large size would be very suitable for sumo. He began pursuing sumo and went on to win the all Brazil amateur sumo competition championship in the free weight category. At this time he believed that, at least in Brazilian amateur sumo, all one needed was size and power to win, and decided to travel to Japan to try out sumo. He was introduced to Tomozuna stable through an acquaintance and joined the stable in 2006. The stable was already home to another Brazilian wrestler, Kaishin. He was given the shikona or ring name of Kaisei Ichirō. Ichirō was the name of Kaisei's late grandfather, who was Japanese.
Kaisei moved through the lower divisions quickly, reaching the fourth highest sandanme division in March 2007. He was promoted to the third makushita division after the March 2008 tournament, but then his progress stalled somewhat. He came through the September 2009 tournament undefeated (although he lost a playoff for the yūshō to Gagamaru) and in May 2010 became a sekitori by earning promotion to jūryō. He was the fourth Brazilian to make the jūryō division after Ryūkō, Kuniazuma and Wakaazuma, but Kaisei was to surpass all of them by winning promotion to the top makuuchi division. After winning the jūryō division yūshō in November 2010 with an 11–4 record, he followed up with an 8–7 at jūryō 1 in January 2011, which saw him reach maegashira 16 in the May Technical Examination tournament.
Kaisei won his first six bouts in his makuuchi debut, the first makuuchi debutant to do so since Takanonami in 1991. He went on to 8–0, the first to achieve that since Sadanoumi in 1980, and 9–0, running neck and neck with yokozuna Hakuhō, before suffering his first defeat to Tochinoshin on Day 10. He thus failed to emulate the great Taihō, who reached 11–0 in 1960. Nevertheless, his final score of 10–5 saw him win the Fighting Spirit Award. He was also given the honour of serving as Hakuhō's tsuyuharai, or dew sweeper, during the yokozuna's ring entering ceremony.
He was promoted to maegashira 5 for the July tournament, where he recovered from 1–4 to go to 6–4, but then lost his last five matches to finish on 6–9. With the intai-zumo (retirement from sumo) of ōzeki Kaiō during the same tournament Kaisei become the heyagashira (the highest ranked wrestler) at Tomozuna stable. Disappointing scores of 4–11 and 6–9 in September and November 2011 saw him fall to the bottom of the division. A 5–10 record in the January 2012 tournament meant he suffered demotion to jūryō in March, but he produced a 10–5 record in Osaka, ensuring a return to makuuchi. In July 2012 he scored eleven wins, picking up his second Fighting Spirit Award and earning promotion to maegashira 1. In September he just fell short with a 7–8 record, losing to Hōmashō on the final day. Since then he has largely alternated winning and losing tournaments. Though he has proven his longevity in the top division, it remains to be seen whether he can achieve more consistent performances. He has not added to his two special prizes and has yet to defeat a yokozuna in 16 attempts.
Kaisei made his san'yaku debut in the May 2016 tournament, having been promoted to komusubi on the back of an 11–4 record from the rank of maegashira 7. He is the second wrestler from Tomozuna stable to reach komusubi since the present stablmeaster took over in 1989 and the first since Kaiō in 1994. After coming through with an 8–7 record he earned immediate promotion to sekiwake for the following July tournament. In the last three tournaments of 2016 he posted losing records and dropped to maegashira 9 before recording an 8–7 in January 2017.
He injured his knee training with Hakuho shortly before the March 2017 tournament and had to withdraw from a honbasho for the first time in his career, bringing to an end his run of 739 consecutive matches from debut, the most among active top division wrestlers. He was demoted to the jūryō division for the first time since 2012 after the May 2017 tournament, but made an immediate return to makuuchi after scoring 10–5 at the rank of Jūryō 1 East in July.
Kaisei's favoured techniques are listed at the Sumo Association as migi-yotsu (a left hand outside, right hand inside grip on the opponent's mawashi), yori (forcing) and oshi (pushing). His most common winning kimarite are straightforward: yori-kiri (force out) and oshi dashi (push out).