“This might be a game, but it’s not something you play.” Akihiko Kayaba, Sword Art Online programmer With no memory of how he got there, Kirito wakes up in a mysterious virtual world, and it’s up to him to find...

Die in the game, and you die in real life. The only way out is clearing the massive floating castle Aincrad. The pinnacle of heroic sagas kicks off here! Source: Yen Press

Based on the 5th main arc.

Young Kazuya happens upon a baby on the mountainside. This baby - Triton - is no ordinary baby. Triton is the last of his kind, but is raised alongside Kazuya in the city as a human. However, the truth is made...