As far as I know, the Japanese didn't field heavier tanks than the Chi-Ha and Ha-Go, which were lightly armed and armored compared to the American M4s, until they began to prepare for for an invasion of the homeland, and those heavier tanks never saw action.
The types of large-scale studies conducted to measure tank casualties by cause and number in the European and Mediterranean theaters don't seem to have been repeated for the Pacific.
Since the Japanese did not field large numbers of tanks capable of challenging the M3 Lee or M4 Sherman, losses to them were relatively light. The major threats, discounting tanks, were mines, antitank guns, artillery, and enemy infantry. Okinawa marked the apex of these tactics, with most, if not all of them being used.
The Japanese made use of a variety of mines, some specifically designed to attack tanks by exploiting weaknesses, such as the Type 99 magnetic mine. Improvised "mines" made of buried aircraft bombs or torpedo warheads with a variety of detonation methods (one of which involved a rock balanced on two poles or sticks; a nearby hidden Japanese soldier would pull on a rope attached to the rock, causing it to fall on the fuze and detonate the bomb) were also used, nearly all of which were capable of completely demolishing a tank and killing the entire crew through concussion effect alone.
As the Japanese placed a low priority on developing larger tanks until the end of the war, their anti-tank assets also lagged behind when facing modern Western tanks such as the Sherman. In the interwar period, the Japanese fielded a 20 mm anti-tank rifle as well as two types of 37 mm infantry guns that could also be used as ad-hoc anti-tank guns; these were obsolete weapons by 1945 and posed little threat to the Sherman except at very close range and from the sides or rear. The Type 1 47 mm anti-tank gun was a modern, small, and easily concealed weapon that was deployed in large numbers. American tanks, particularly on Okinawa, suffered badly from them, especially when drawn into areas that made it difficult or impossible to maneuver; the gun wasn't capable of penetrating the Sherman from the front at any range, but could do so from the sides or rear at well over 1,000 yards. Japanese anti-tank gun units apparently took great pride in their marksmanship; a group of four American tanks was knocked out with only sixteen shots. Large-caliber artillery, rockets, and spigot mortars were also used to attack tanks, but posed little threat unless a direct hit was achieved. Japan had developed experimental weapons analogous to the American bazooka (Type 4 70 mm Anti-tank Rocket Launcher) and German Panzerfaust (Type 5 45 mm Recoilless Gun), but they did not see any action before the war ended.
The Japanese made extensive use of infantry to attack tanks directly, often at the cost of their own lives. A number of weapons were developed for this purpose, including satchel charges and various types of hand-placed mines and shaped-charge weapons. Japanese infantry would also attempt to climb on top of U.S. tanks, force the hatches open, and throw grenades inside once the supporting infantry had been killed or driven away and the tanks disabled.
These squads of three to nine men did not cause as many tank casualties as the 47-mm. gun, but they continued to be a constant source of danger. Each man of the squad had his own job: one would blind the tank with smoke grenades, another would force it to button up by hurling fragmentation grenades, another would immobilize it with a mine under the track. The final act was destruction of the tank and crew by a satchel charge.
Tanks without infantry support are extremely vulnerable to close-in attack, and the Japanese exploited this on several occasions during the Pacific war, especially the April 19, 1945 attack on Kakazu Ridge;
On Okinawa, one U.S. Army tank battalion, the 193rd, supporting an infantry battalion of the 27th Division, suffered extremely from a lack of tank-infantry coordination during a one-day attack. Of thirty U.S. Army tanks, three were stopped by mines or road hazards and five were shot by Japanese anti-tank guns enroute to the village objective. In the village, fourteen more tanks were disabled by mines, anti-tank guns, artillery, and close assault units. Six more tanks were attacked by suicide attackers who swarmed the unprotected tanks and destroyed them with satchel charges. At 1330, the tanks withdrew. Only eight vehicles of the original thirty made it back to the start point. The tanks had operated wholly without infantry support.
The two Marine tank battalions employed on the island, the 1st and 6th, took it even further like they had in previous battles. The Marine tankers attached long nails or chicken wire cages to their tanks' hatches to prevent explosive charges from touching them directly, and used poured concrete or wood planks (or both) on the tanks' sponsons to prevent Japanese magnetic mines from sticking. Some Marine tanks also had wood or metal bars attached over their suspension bogies to deflect thrown explosives and prevent them from rolling underneath the tank to its vulnerable belly, as well as spare tracks attached to the turret or hull to provide additional protection from antitank fire.
A device known as the "backscratcher" was developed by the Ordnance section of the U.S. Tenth Army prior to the battle to clear away Japanese infantry on or near friendly tanks. It consisted of five M2A1 bounding antipersonnel mines fixed to the outside of a tank's turret that could be fired from the inside of a tank. Only 30 kits were constructed, and they were only mounted to a handful of tanks, achieving mixed results. The 713th Tank Battalion (Armored Flamethrower, Provisional) coated their tanks with a paint mixed with sand in the hope of defeating Japanese magnetic mines, but these mines weren't encountered by the battalion. Late in the battle, Army maintenance units began to cut armor plate from wrecked tanks and place it on hulls and suspensions in order to ward off hits from Japanese antitank guns, but these efforts proved to be too cumbersome and were mostly abandoned.
Replacements for a number of light and medium tanks which had been lost were requested on April 28, 1945, but they did not arrive until after the battle had ended. Four light and 147 medium tanks were written off up to June 30, 1945.
American armor, which played so important a part in the ground action, had suffered heavily. By the end of May, not counting Marine tank losses, there had been 221 tank casualties in the four Army tank battalions [193rd, 706th, 711th, 763rd] and the one armored flame thrower battalion [713th]. Of this total, 94 tanks, or 43 percent, had been completely destroyed. Enemy mines had destroyed or damaged 64 tanks and enemy gunfire 111. Such mishaps as thrown tracks or bogging down in bad terrain had accounted for 38, of which 25 were subsequently destroyed or damaged, mostly by enemy action. The 221 tank casualties constituted about 57 percent of the total number of Army tanks on Okinawa. At least 12 of the valuable and irreplaceable armored flame-throwing tanks were among those lost.
The 193rd Tank Battalion, crippled after the botched Kakazu Ridge attack, was effectively disbanded, with its remaining tanks going to reinforce the other three regular U.S. Army tank battalions on the island due to a lack of immediate replacements. The Army, not expecting heavy tank losses, had only planned for a small immediate reserve of 13 medium tanks on Saipan. These were ordered on April 25, 1945, but had never actually been moved to Saipan to begin with. They had to be shipped from Hawaii and didn't arrive until ten days after the battle was over, on June 10. 65 Shermans and 25 tank recovery vehicles were ordered from Hawaii for the long term on April 28, but these didn't arrive until July 15!
Due to the heavy tank losses on Okinawa, especially to concealed 47 mm guns, American tankers requested a vehicle with heavier armor (to better withstand hits from all sides) and a higher-velocity gun (to engage enemy guns from further away). Twelve M26 Pershing tanks were ordered to be sent to Okinawa while the battle was still going on, but did not arrive until well after it had ended, on July 21. It is interesting to speculate how these tanks would have performed. Okinawa had poor or nonexistent road conditions even before fighting began, and the Pershing had underwhelming off-road performance (besides its lowered ground pressure compared to the Sherman) and was prone to mechanical breakdowns due to its overtaxed engine and transmission. These tanks were later used by the 193rd and 711th Tank Battalions for pre-invasion training on the island.
Sources:
Hunnicutt, R.P. Pershing: A History of the Medium Tank T20 Series. Novato: Presidio Press, 1971.
Hunnicutt, R.P. Sherman: A History of the American Medium Tank. Novato: Presidio Press, 1978.