Its not that strange, the European Zweihänder was also for anti-cavalry tactics.
Shields lasted in Korea until the Joseon period (1392–1897) But I have noticed shields in Asia are less common than in Europe
In Japan Shields died out in the Nara period (710–794)
There are wooden shields dated to the Yayoi period (300 BC-300AD) and several iron shields dated to the the Kofun period (250–538) but after that they stop existing.
It could be because, horses introduced in the 5th century changed Japanese tactics, the bow became an important weapon. During the Kofun period phalanx-like tactics were imported from China. When Yamato court unified Japan during the Nara period, their last major enemies in the north were known for their horse tactics, although paintings do show wooden shields.
Other factors could be, the favorite Japanese weapons required two hands, and that they never developed the shield straps that Europeans did meaning their power thrusting would be cut in half, and Japanese armor from early times had large shoulder protect and wristbands so they no longer needed shields.
Archers often carried a type a shield they could stand up and shoot behind. But by the middle-ages shields were gone.