The children of the wealthy go to Shinryou Private Academy. One day, the most beautiful and popular girl at school, Riku Rei, encounters the protagonist of this story, Suigin, who is a poor boy with no family.
The poor student, Suigin, spends most of his days working various part-time jobs, and his only skill is gaming. Suigin meets Riku Rei through an online game. However, since Suigin is playing the game for free, their correspondence is limited.
Suigin finds out that his only way of interacting with Riku Rei is about to end. Suigin ends up in utter shock. However, in the game, Suigin promises Riku Rei to do everything he can to find the flower she is looking for in the game before it ends.
On the last day of services for "Dungeon Century," many of the players gathered to enjoy some last-minute festivities. Riku Rei waits for Suigin to arrive, but ends up going to find the flower herself because he's taking so long.
Riku Rei summons Suigin after her father, Riku Yuuki dies, and hands him something that Yuuki apparently left for him. Suigin hesitantly accepts the item: a specialized console to play the new game "Grave Buster."
Riku Rei is taken by some debt collectors, and Suigin follows them. However, Riku Rei's captors immediately get away by car. Suigin somehow manages to catch up on a bike, but she is then taken away by a mysterious man who magically disappears.
Suigin is pulled into the world of "Grave Buster" by a woman named Twin Star. Surprisingly, Suigin ends up meeting his grandfather, Riku Yuuki, who should've been dead, and he can't hide his doubts about this whole situation.
Riku Yuuki explains the game of Grave Buster to Suigin. In the game of tomb raiding and tomb guarding that has gone on for years, Riku Yuuki ended up being the one and final guardian to guard the Goddess's tomb.
Suigin receives a message from Temujin, the man who kidnapped Riku Rei, who tells him to come to Grave Buster. Suigin must come up with a plan to save Riku Rei as soon as possible!
Riku Rei undergoes a certain ritual and joins Temujin's group. Meanwhile, Suigin encounters a young boy named Takeshi, who ends up crashing a martial arts tournament and accidentally drags Suigin and Twin Star with him.
Suigin takes Takeshi's place and fights in the tournament. However, he faces a penalty and ends up having a difficult battle against his enemy. And then the Twin Star reveals their true form and powers!
