OVA
Description
Chōun Shiryū, alias Sei, is a blue-haired, red-eyed warrior renowned for her spearmanship and strategic acumen as a general. Originally serving under Kousonsan, she confronts the Yellow Turbans alone, inflicting heavy losses before being overrun. Rescued by Kan'u through Koumei’s intervention, she allies with Kazuto’s faction under the condition of seeking a superior master during her travels. After the Enshou conflict, she commits permanently alongside Kouchuu.

Her narrative diverges across routes: in the Gi route, she saves Kazuto from bandits and later joins Shoku following Kousonsan’s downfall, while the Go route integrates her into wider faction struggles. Adopting the tokusatsu-inspired alter ego Kachou Kamen ("Butterfly Mask"), she dons a mask with unchanged attire, delivering dramatic speeches and acrobatic feats. Though her identity is transparent to Kazuto and Koumei, OVAs humorously depict her transforming into a giant Ultraman-esque figure.

Balancing calm composure with playful flirtation, Sei harbors a volatile streak when provoked over menma or alcohol. The visual novels portray her as blunt and chaos-inducing within Kazuto’s harem, while the anime exaggerates her eccentricity with perverted humor and delusions. Initially naive about intimacy after observing soldiers, she grows adept and openly endorses Kazuto’s polyamory, including threesomes with Kan'u.

A master of agile spear techniques, she contrasts peers like Chouhi through precision over brute force. Skilled in hand-to-hand combat, horsemanship, and leading commando-like troops, she excels in tactical flexibility and governance but occasionally favors covert methods. Weaknesses include lesser physical strength, egocentric monologues, and communication hurdles from her quirks.

Pivotal developments include her pregnancy with Kazuto’s child in *Shin Koihime†Eiyuutan* and involvement in spin-offs like *Shin Koihime†Musou -Kakumei-*. Her design echoes Rei Ayanami and Tatenashi Sarashiki, featuring short blue hair and a Spear-of-Longinus-inspired weapon. Trivia notes her menma fixation, chuunibyou traits, and a censored "disturbing face" in the anime that unnerves characters.