The KT harbor is way more expensive, but also way tanky, which might influence Japanese to not open for the dark age, which is something you often expect from them even on water maps.

Knights Templar have so much wood income that they can keep up in archer count against the Yumi archers from the Japanese, which are cheap and easily massable. Keeping up in mass with a more expensive and robust archer unit means prolonged Feudal age might not be in Japan's best interest.

If Knights Templar go Knights Hospitaller, their villagers get bonus health and movement speed, making it harder for Japanese to get kills with raids.

Genoese Crossbowmen are a strong counter to Japanese infantry units, doing a lot of damage to them.

This is something Japanese have struggled with in the past, right? Knights in the feudal age. They can be better now than ever before, I would say, in contesting in that feudal age up against even knight civs thanks to the cheaper cost of the Yumi, such a strong archer when you reach critical numbers, especially aided by the Yumi Bannerman for additional damage. And the longer-lasting food of Japanese courtesy of the Kura Storehouse and the good berry gathering rate with the upgrade means they can really put up a fight in feudal ages even though they might have a composition disadvantage against these knight civs in particular.