Manabu Naoi is a supporting character in the Haikyu!! series who serves as one of the coaches for the Nekoma High School boys volleyball team. He is a 26 year old alumnus of Nekoma, having been a member of the volleyball team during his own high school years. After graduating, he returned to the school to help coach the team, working alongside the veteran coach Yasufumi Nekomata and the team's main players. In terms of appearance, Naoi has a rectangular shaped head with a jutted jaw, short dark hair, and dark eyes. He has a stout, muscular build that gives him a tough exterior. Despite his intimidating looks, a notable personal detail is that he cannot handle alcohol well. Naoi's personality is marked by confidence and a competitive streak. He has a slight rivalry with Keishin Ukai, the coach of Karasuno High School, whom he knows as an old acquaintance. During the period when both Naoi and Ukai were active players, exchanges between Nekoma and Karasuno were at their most frequent, and the two coaches once made a promise to meet on the national stage together. This personal connection adds depth to the long standing rivalry between the two teams. His motivations are rooted in a desire to uphold Nekoma's traditions and guide the team to success, particularly in fulfilling the long held dream of facing Karasuno in an official match, an event known as the Dumpster Battle. Within the story, Naoi's role is primarily that of a coach and supportive figure for the Nekoma team. He provides guidance and strategic input during matches, though he operates somewhat in the background compared to the more prominent coaching figures on either side. His key relationships include his bond with the Nekoma players, particularly the team captain Tetsuro Kuroo and the setter Kenma Kozume, as well as his friendly rivalry with Ukai. In terms of development, Naoi represents the continuity of Nekoma's volleyball program, bridging the past and present as a former player turned coach. He does not display any flashy or supernatural abilities; his notable skills lie in his knowledge of the game, his experience as a former player, and his ability to help prepare the team for high level competition. His presence reinforces the theme of legacy and the importance of those who support the players from the sidelines.