Is it a Type 4? I recall there was a project on fitting Garands with magazines so I'm not sure here.
Chikuma's rifle's though. It looks semi to me, but I don't recall Type 4 or any WW2 era semi rifle looking like that....

On second thoughts, Chikuma's rifle seems to be another Type 4 too. Though the magazine doesn't look so.

At right is indeed a Type 4, at left is one variant of the Shisei jidō shōjū kō-gō (試製自動小銃甲号), typically referred to in English as the "Japanese Pedersen". [1] [2] [3]