A long time lapsed, in 1942, Japanese Army were seeking new infantry Anti-Tank weapons. They were already developed 13mm manual loading Anti-tank rifle as experiment, and then Type 97 automatic ATR, Type99 Magnetic Charge (known as "Turtle Mine"). But these weapons were too heavy, expensive, or weak.
In 1943, Japanese forces imported the H.E.A.T. technology from Reich. It was good solution for infantry Anti-Tank weapons because its performance not depend on projectile velocity. Long and heavy barrel for high velocity is no longer required. They developed new weapons like Type2 40mm Rifle Grenade and Type3 Anti-Tank Grenade forthwith.
However, It caused new problem. High penetration H.E.A.T. projectiles had larger diameter, so it becomes too heavy for firing as rifle grenade. The army also tried to fire huge grenade from Type97 ATR, but this solution can't avoid the ATR's high cost and heavy weight.
At this time, Japanese forces encountered American Bazookas. Its projectile has thrust power, so it provides heavy weight projection ability to infantry without heavy huge gun. Also Panzerschrecks were imported about these time. They had set a course of Japanese new Anti-Tank weapons.
Actually, rocket weapons were not something new in Japanese army. They had already started rocket weapons development in 1932. These weapons was completed in 1943, with 7cm, 9cm, 15cm, 20cm, and 24cm version. But they fell into disrepute because of bad accuracy. Though, using rocket in infantry combat not needs very accuracy. So, Japanese new H.E.A.T. projector was developed on experienced Japanese 7cm and 9cm rockets.
Well, rocket projectiles has two way of stabilization. One is fin stabilized, the other is rotate stabilized. Rotate stabilized rockets were less influenced by wind. but warhead rotating causes bad effect to the penetration capability.
Around that time, that effect was not well known, so the army chose accurate way. In experiment, the rocket penetrated 80mm armor. It was not so good as Panzershcreck or Bazooka, but it had been considered that still effective against sherman tanks. The rocket and launcher passed trial, and adopted as "Type4 7cm Rocket Propelled Armor Piercing Grenade" and "Type4 70mm Anti-Tank Rocket Launcher". The rocket reached 160m/s, that was faster than Bazooka and Panzerschreck, and its hit ratio was estimated 60% at 100m distance. Its propellant was burned short time after fired from barrel, so gunners must wear face mask.
The launcher was based on Bazooka and Panzerschreck, but it had some improvements. It had bipod for stable firing in prone position. And its barrel can split-off to two part for better mobility. The barrels was connected by three thumbscrews. Unlike competing weapons, rockets was ignited by striking pin, because it was easy to mass-production than electric devices in Japanese factories. Its maximum range was estimated as 750-800m, but effective range is 50-100m. So the sights has two holes for these distance.
Also there was planned 9cm variant to improve performance. It has 120mm penetration, but the rocket's velocity was reduced to 106m/s because of its weight. These rockets was expected as not only anti-tank weapons, but also replacement of mortars in paratrooper. And about 3500 units was produced in Osaka and Ogura Arsenal, but not entered war.
In game, its bipod provides better accuracy in prone position. And, while its penetration performance not so great, because of heavy charge, it gives very serious damage if penetrated. You will see this weapons mainly in Japan main land map, and it replaces some of "captured Bazooka" kits.