Versus II is on Dengeki MAGAZINE Volume 40
Versus II (バーサス II, Bāsasu II?) is the second and final part of a crossover story between the Sword Art Online and The irregular at magic high school series.
This part of the crossover was written by Kawahara Reki, the author of Sword Art Online, supervised by Satou Tsutomu, the author of The irregular at magic high school.
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Kirito found himself inside a pure white sphere, instead of a forest where he should have appeared. Although Kirito had asked to use a default avatar, he found that he looked exactly like his avatar in ALfheim Online. Just as Kirito voiced his complaint about the situation, he heard another person responding to him. Kirito was about to draw his sword when he realised that he had already met with the person before. Although the man wore a school uniform that Kirito had no memories of, he recognised the man as being the mysterious character who had taken the role of the giant Beli in a quest in ALO.
After Tatsuya explained that they were inside a virtual simulation, he decided to tell Kirito his real name and then considered whether he should take the same measures to deal with his own world connecting with Kirito's. However, Kirito claimed that there should be other measures that would overload the simulator and break the connection. Kirito then recalled his conversation with Suguha in the morning and came up with the idea to have the simulator decompose a very large number into prime numbers. He began flying by using his fairy wings and, after Tatsuya followed him, Kirito shared his idea with Tatsuya. However, to Kirito's shock, Tatsuya handled the decomposition via mental arithmetics in a brief moment, causing the world to collapse.