I've heard about Shota and Ryuhei's dad (thanks to Deka Wanko which made lots of references to Taiyo ni hoero). I have yet to see him in a drama or movie though. So far, only two Mahoro books have been published. But Miura Shion is said to be working on the third installment, with some new stories serialized in weekly magazine Shukan. Title I believe is "Mahoro Ekimae Kyōsō-kyoku." But that was in 2010 to 2011, though. No new developments as of yet, maybe because she was busy with Fune wo amu.
Re: Yusaku matsuda
So far, only two Mahoro books have been published. But Miura Shion is said to be working on the third installment, with some new stories serialized in weekly magazine Shukan. Title I believe is "Mahoro Ekimae Kyōsō-kyoku." But that was in 2010 to 2011, though. No new developments as of yet, maybe because she was busy with Fune wo amu.