SPOILERS info to help

Dave, his brother Hyde, and two more, Kiada, and Bhan are a group of people brought together to complete reborn. reborn is a game Dave originally created as a fun game world with dive technology. 

the game reborn was later changed to help house 138 girls that were killed and stuck inside of a game called Second Life. one of the 138 girls was Dave's best friend and he couldn't save her, so dave and the other three spent hundreds of years inside of the game in frame jack protecting the girls for Reginold, the creator of second life and its associates( time moves faster in the game than in the real world)

the plan was to transfer the girl's sparks into reborn and then the four leaders would just have to complete the game and shut it down from the inside. this will put the game in an endless rising frame jack, allowing them to live on with the girls for eternity that is stuck in a single moment.

but something happened when they entered the game. Reginold somehow got into the game before dave and the others and messed with everything, placing blocks everywhere to restrict the flow of information to the leaders and basically leaving them blind in the game.

harem reborn picks up off at their 5th attempt to beat the game because the game resets itself every time Reginold gets close to the administration key to control the game. Dave has been beaten down the worst because of Reginold's hate for what dave did to him inside of Second Life. Now, Dave is stuck trying to get his memories back and try to beat the game.