Japan got shaped charged technology from Germany in 1942. Mission resulted in development of Type 2 rifle grenade launcher and AT grenades.
Report from Kiska battle, lists some weird 70mm mortar, new model of grenade, and knee mortar.
Report from Tarawa battle indicates, that SNLF employed MGs in pairs, and every was supported by knee mortar (that is probably why reported SNLF structure have so much support weapon in US report).
Ocean Divisions got their squads divided into two sections. There will be lots of work to model this, but it should result in almost doubling AV for Division (with poor firepower). Also, reports indicate that 20mm AT Rifles were employed excessively, although Taki claims, that they were removed entirely from use early in the war. There are reports, that Squads in China were also divided.
And lastly, most of semi-automatic Rifles were send in last transport to Okinawa (but I don't know if they reached destination).
Anyway, you have Type 100 grenade discharger, Type 2 rifle grenade launcher, Type 4 70 mm AT Rocket Launcher, and SMG 100, which were produced in large enough numbers to use.