If you're looking for manga similar to Over Image, you might like these titles. All recommendations are made by Anime-Planet users like you!
In a world where everyone connects to an online network, pudgy Haruyuki Arita can't seem to catch a break. Constantly bullied, afraid to face reality and paranoid his two childhood friends pity him, the teenager uses online games as a way to escape his problems. But things change one day when Haruyuki's beautiful upperclassman Kuroyukihime approaches him with a mysterious time-decelerating program known as Brain Burst - there‘s just one catch. To keep the ability, he must defeat other Brain Burst wielders in Accel World, an exclusive, virtual MMORPG, and the newbie player will need all the help he can get. Eager to prove he's not a pathetic weakling, Haruyuki joins forces with Kuroyukihime to challenge fierce competitors and discover just how incredible Accel World and he truly are.
In both series school kids are taking part in some sort of fighting game. The fighting takes place in a virtual reality of sorts and losing and winning seems to carry benefits and penalties to the real world.
In short, it's similar stuff, so if you liked one, you'll probably going to like the other one too.
Many similar points in plot (many of which are spoilers), but I guess I can reveal that it features some guy "starting" to play a reality bending game and some girls who claim to know him, but whom he can't remember. The girls in question "introduce" him to the game, but all is not as it seems. Other than that Over Image has probably better art than Baroque Knight, but the second is much more fun.