SONS OF NIPPON-GO
"Nippon-Go exhibition" also has photos of planes that used to belong to Aviation Department of The Mainichi Newspapers. This is a Mitsubishi MU-2B turboprop named "New Nippon", a son of Nippon-Go who inherits genes of Mitsubishi planes.
This Piper was named "Gyosei (Dawn star)." Coincidentally it has the same name as the one for fictional newspaper company modeled on The Mainichi Newspaper which was featured in "Tsubasa wo kudasai~Freedom in the sky", Maha Harada's novel based on Nippon-Go story.