Trained defenders, known as Bastioners, employ the enigmatic power of Aegis to confront otherworldly invaders. Aegis boasts the ability to endow people and objects with formidable strength, but individuals cannot utilize this power on themselves, thus requiring pairs to harness its potential.
Yorino Aratsugu and Yoko Kaminoi, two young girls, aspire to become skilled practitioners of Aegis. Yorino once shielded the meek Yoko from bullies, however, Yoko has now outshone her in every regard, except combat proficiency. As they approach full-fledged Bastioner status, Yorino faces the challenge of not being outshone entirely by Yoko's aptitude, all while grappling with complicated emotions for her longtime friend.
