Ww2 imperial Japanese sweater & underwear 2set

All three items were found together. The light cotton V-neck jumper may be underwear, and only one piece of underwear (trousers) has the Kaiyosha stamp.

Kaiyosha was a friendship organisation of army officers who were famous for the manufacture and sale of military equipment.

Basically, both three items are unused, but they are of the diameter of the old days, so please understand.