Minamoto Nakago is the Yondaime Tsuchikage, engaged to Naruko and also part of the main interest of an umbrella club -Mysterious Blonds. Wait, what? He's not even a Konoha-nin -how did he form a club?! He doesn't even have a FC ID card!
This club is to support Naruko in her dream of becoming Hokage, and believing she can do it. She's always declared it (sometimes very loudly) and continues to believe she could do it and is determined that one day soon she will be.
Head to the Ninja Academy and then look for the administration part of the building. If you need any assistance, go to the front desk.