Blue Angel (book)
Blue Angel is a book in Yu-Gi-Oh! VRAINS featuring a protagonist of the same name. Akira Zaizen used to read the book to Aoi Zaizen when she was younger to comfort her, which inspired Aoi to adopt the name for her online persona.
According to Spectre, the book is a story about an angel who lived a lonely life due to her cold-hearted personality. Although she acted tough, the angel by herself cried due to loneliness, shedding teardrops with color of blue. When she was attacked by the evil monsters, her fellow angel comrades come to her aid. Through the battles, she learned of friendship and kindness, and changed for the better, gaining friends who fill the void in her heart. However, for reason unknown, the angel continues to shed tears as she vanquishes the evil monsters.
According to Aoi, the book's story resonates strongly with lonely people, yearning for love and attention. Since she was one such case, she used this reasoning to claim that Spectre was just like her since he also liked the story quite a lot. He in turn confirmed this was indeed the case.