If you're looking for manga similar to A Certain Magical Index SS: Love Letter Soudatsusen (Light Novel), you might like these titles.
Daisy meets Lee Jiang-yu, a student from Hong Kong, at the university for the first time, who invites her to Professor Rob McCoy's lab, where the other Wild Bunch members are gathered. There, they gradually help with the creation of a parallel world inside a computer network, inhabited by digital monsters. Dolphin asks for the help of his 10 year old gamer son, Keith, who eventually creates the rudimentary beings and organizes them by various criteria: abilities, power level, etc. Daisy works on the Ark...
A mysterious planet appears over Earth, bringing with it unparalleled bliss. If you can afford the space trip, that is.