这是有关各式各样的人们取回什么的温馨故事，同时也是有关斗争的故事。
主人公桐山零，幼时因为意外事故失去了家人，是一个背负着沉重的孤独的17岁将棋棋士。 独自居住在东京旧市镇桐山零遇见了明里、日向、桃三姐妹，少年桐山零因此发生了改变……

十七岁的桐山零（河西健吾 配音）是一名将棋棋士，悲惨的童年遭遇让他自幼便失去了家人，这么多年来一直背负着沉重的记忆独自生活，长此以往，零已经习惯了压抑自己的感情，在心房周围筑起了无法撼动的高墙。
某日，零邂逅了川本家的三姐妹——温柔体贴，擅长照顾他人的大姐川本明里（茅野爱衣 配音）、个性开朗乐观，非常不擅长料理家事的二姐川本日向（花泽香菜 配音）和还在上托儿所稚气未脱的小妹川本桃（久野美咲 配音）。三姐妹的出现让零再度感受到了家的温暖，找回了久违的快乐。与此同时，二海堂晴信（冈本信彦 配音）、三角龙雪（杉田智和 配音）和松本一砂（本村昂 配音）等强劲对手的出现，亦令零燃起了对将棋的热爱于斗志。

In the year 2022, a massive online role-playing game called Sword Art Online (SAO) is launched. With the aid of "NerveGear" technology, players can control their avatars within the game using nothing but their own thoughts.

Kazuto Kirigaya is among the lucky few who get their hands on the first shipment. He logs in to find himself, with ten-thousand others, in the scenic and elaborate world of Aincrad. However, in a cruel turn of events, the players soon realize they cannot log out; the game's creator has trapped them in his new world until they complete all one hundred levels of the game.

In order to escape Aincrad, Kirito will now have to interact and cooperate with his fellow players. Some are allies, while others are foes. Sword Art Online is not all fun and games: if they die in Aincrad, they die in real life. Kirito must adapt to his new reality, fight for his survival, and hopefully break free from his virtual hell.

The story centers on Koyomi Araragi, a third year high school student who has recently survived a vampire attack, and finds himself mixed up with all kinds of apparitions: gods, ghosts, myths, and spirits.