Kokoro Connect Vol. 4 (manga)

For the past month, five high school friends have been randomly swapping bodies as part of a mysterious alien experiment. But now it seems that the experiment has run its course and things are slowly going back to normal. One of the group, Yui, even gets to go out on a date...with another girl! Her friends, of course, can't help but tag along to see how it goes. Will Yui's friends ruin her chance at romance?

The group soon realizes it has bigger things to deal with when it becomes apparent that the enigmatic being controlling their lives isn't finished with them yet. A new experiment is about to begin...