There are many secret characters you can only unlock from hidden objects or certain situations in Date Everything!. Finding these characters is generally pretty tough since you likely don't know the right conditions to summon them, as is the case with Reggie.
Reggie is a fairly tricky guy to meet, but he's the final number in the basic Date-A-Dex, which means he's a must-meet if you want to unlock all entries. Once you know what needs to be done, he's easy enough to track down, so here's how to find Reggie in Date Everything!.
