Desperately Seeking Brains!

Mutsumi Saburo, a senior at Natsumi's school (who just so happens to be Natsumi's love interest), is trying to approach her. Meanwhile, the Keroro platoon is trying to find its fourth member, even if it means scanning through all of Japan and its giftshops! But while Fuyuki starts to have suspicions that Mutsumi could be one of the infamous Men in Black, Mutsumi comes into the household at an incredibly fast pace, and his entrance is also completely suspicious. Is Mutsumi really a Man in Black, or is he the partner of someone incredibly special?
Aki is turned into a teenager by Kururu's new weapon - What If I Can Do Over My Life gun - and takes the opportunity to revisit her youth by going to her children's school. However, in Fuyuki's uniform, she is harassed and soon causes trouble for her son, as everyone thinks she is him. In the meantime, Keroro must find Aki, within 3 hours, or else the damage will be permanent.