User blog comment:Mizuki Raimon/What do you think they're gonna be doing 10 years later?/@comment-2235609-20110723171456/@comment-3976990-20110723182758

Who will be the third hard to say but he wil be from next generation. That means he will be the same age as Endou/Natsumi son/daughter. And fourth protagonist will be Endou's grandson.