Harunobu Nikaidō (二海堂 晴信 Nikaidō Harunobu) is Rei's friend and main rival in shōgi.
Nikaido comes from a wealthy family, but he is born with an incurable disease. He met Rei a long time ago and since then Rei has known him for a long time. He sees Rei as his best friend and rival in shogi.
Despite illness having plagued his childhood, Nikaidou has an earnest personality, along with a cheerful outlook towards life. He is described as persistent and stubborn when it comes to his rivalry in Shogi with Rei. However, he does get emotional over his losses, but does his best to keep a strong front while in public. He doesn't give up and even with his illness lets shogi become his life.
|Rei Kiriyama • Akari Kawamoto • Hinata Kawamoto • Momo Kawamoto • Someji Kawamoto • Misaki • Mikako Kawamoto|
|Kai Shimada • Harunobu Nikaidou • Morio Shigeta|
|Masachika Kouda • Kyouko Kouda • Ayumu Kouda|
|Touji Souya • Raidou Fujimoto • Sakutarou Yanagihara • Kengo Kumakura • Masamune Gotou • Takeshi Tsujii • Kenji Dobashi • Gakuto Sakurai • Izaya Namerikawa • Okuyasu Yokomizo • Tatsuyuki Misumi • Irie • Subaru Hachiya • Yasui • Shouichi Matsunaga • Issa Matsumoto • Junkei Yamazaki • Takanori Jinguuji • Shichirou Tanaka • Hiroshi Yamanami|
|Takashi Hayashida • Eisaku Noguchi • Tsugumi|
|Yuusuke Takahashi • Chiho Sakura • Kokubu • Megumi Takagi|
|Hanaoka • Seijirou|