Sword Art Online Re:Aincrad, Vol. 3 (manga)

This might be a game, but it's not something you play.After saving the Moonlit Black Cats, Kirito is drawn to their warmth and camaraderie, which persist even in the bleak world of SAO. He sets aside his "beater" identity and joins their ranks. With Kirito's help, the formerly weak guild makes quick progress and seeks out more powerful foes. But Sachi, the guild's only female member, is on the verge of a breakdown, living in constant fear of death, and she wants desperately to escape the game world. So when she suddenly disappears one night, Kirito rushes out to find her, fearing the worst...