I think in ch8 page 14 when his grandfather said "this place is a place that only you, you...

I think in ch8 page 14 when his grandfather said "this place is a place that only you, your deceased grandma and i know about." I think its Motoharu and Akira who only know about that place..... Motaharu is the profesor and Akira is the grandfather they have a manga Hana no Miyako de