It was the start of bombing campaign that would see key Japanese cities, infrastructure and industries reduced to ashes through conventional and firebombing raids.

With the aircraft industry being a priority target, the Imperial Japanese Navy Aviation Bureau (海軍航空本部, Kaigun Koku Hombu) looked to ways to combat the B-29 menace.

One concept was a point defence interceptor that could quickly rise to meet the bombers and so the Mizuno Shinryū was born.

In November 1944, the Navy Aviation Bureau looked into the possibilities of an aircraft to undertake suicide missions (神風, shinpu).

The Bureau envisioned that gliders would be launched with rocket boosters from caves or shore positions and pilots would guide the aircraft and the 100 kg (220 lb) explosive payload inside it into Allied ships or tanks should the Japanese home islands be invaded.

A number of concepts were discussed and sketched and after much deliberation among Akita and his teams the design was complete by May 1945, and the Mizuno Corporation, a small glider manufacturer better known for sports equipment, had almost finished the prototype.

The straight and flat wings were wide but had a short span and were designed to ensure that the glider was easy to handle given that inexperienced pilots would be at the controls.

Tashiichi Narabayashi was the pilot who flew the maiden flight in mid-July 1945 at the airfield in Ishioka, a city located in Ibaraki Prefecture, about 90 km (56 mi) northeast of Tokyo.

The Jinryū was towed into the air by a Tachikawa Ki-9, piloted by Saburo Fujikura, a man known for his skill in flying gliders prior to the beginning of the war.

When Narabayashi put the Jinryū into a dive and had reached 300 km/h (190 mph), the glider began to vibrate to such a degree that he was unable to read the gauges.

Here, the Jinryū was modified to accept a group of three Toku-Ro I Type I rocket engines that together would produce 300 kg (660 lb) of thrust during a 10-second burn.

In addition to expressing his doubts about the rocket engines, he also stated that the Jinryū would be unsuited for shinpu missions because, despite the changes made to the glider to improve the flight characteristics, it was a challenging aircraft to fly.

He estimated that at maximum burn the Jinryū could attain a speed of 750 km/h (470 mph), and for weapons he envisioned that it could carry ten explosive charges adapted from artillery shells used by the IJA in their 100 mm (3.9 in) guns (likely the Type 92).

Two people were retained from the Jinryū project: Sakakibara, the lead designer, and Yoshio Tonsho who would oversee the construction of the prototype.

Since the average Japanese pilot had little experience with canard equipped aircraft, the Shinryū II had spoilers fitted into the top of each main wing.

The aircraft would have been far more complex to build than the Toka or Ōka and the Shinryū II was constructed for maneuverability, high altitude operation and the means to land.

In addition, using the Shinryū II for shinpu missions against tanks makes little sense when there were other simpler and more effective means (both already in service and under development) to eliminate armour.

As an interceptor, the Shinryū II had a similar role to the Mitsubishi J8M Shūsui and the German Bachem Ba 349 Natter, which the Japanese were aware of and obtained data on (although the plans never made it to Japan).

Like the J8M and Ba349, and due to the limited range afforded by the rocket engines, the Shinryū II would have to be positioned close to targets that were likely to be bombed.

Unlike the J8M which burned up all of its fuel at once, the Shinryū II had a second set of rocket engines which could be used to sustain flight endurance or to increase speed during the attack.

In the same way as the Ba349, the Shinryū II would be armed with rocket projectiles, likely fired as a group to affect a spread pattern, to bring down the bomber target.

Finally, akin to the J8M, once the fuel and ammunition were expended, the Shinryū II would glide back to its base to be recovered, refueled and rearmed.