Masaomi Arikawa, childhood friend and classmate of protagonist Nozomi Kasuga and elder brother to Yuzuru Arikawa, becomes temporally displaced from both during a dimensional rift, emerging in an alternate world three years before their arrival. Initially masquerading as a Genji clan ally, his true allegiance lies with the rival Heike faction, where he operates under the alias Kaeri naifu—a moniker synonymous with battlefield dread. His position as Ten no Seiryū (Heaven’s Azure Dragon) intensifies this friction, as the role traditionally belongs to the Genji-aligned Hachiyō.

A complex undercurrent of unspoken mutual attraction defines his bond with Nozomi, symbolized by his gift of a rare musical pocket watch reflecting her tastes. While their animated counterparts deepen this emotional thread, their interactions stay tempered by clashing loyalties. Balancing protective instincts with tactical brilliance, he maneuvers through political strife to shield loved ones without compromising wartime objectives.

Charisma and reliability anchor his command of Heike forces, yet internal conflicts arise when duty clashes with personal ties—particularly when decisions risk harming Nozomi or Yuzuru. Prolonged isolation in the alternate timeline underscores his adaptive resilience, revealing a strategist willing to negotiate ideals for survival. His narrative arc persistently intertwines factional obligations with unresolved emotional stakes, driving pivotal choices in the overarching conflict.