Almost a month in this new patch, games with chickens improve early game and having the samurai be useful is nice and drushing in the dark age is easier with the militia line food discount.
Gambesons should affect all infantry, even the spearman line, they get destroyed by arrow fire and infantry unique units such as Berserkers and Samurai could use a bit more pierce armor.
But I think reworking the team bonus +4 line of sight on galleys to +4 on dock units, making fishing ships find food easier and team mates with unique warships such as thirisadai (Dravidians) and longboats (Vikings) enjoy this bonus.
Add heated shot to boost their Yasama usage and defend docks, destroying enemy ships with towers could become an option to secure fish traps.
Tweaking heated shot to gain bonus against siege is totally fine also, a line of defense for the Japanese against siege pushes in land maps such as black forest.
A final university to add is architecture, Japanese boast unique architecture, enough said, swap it out with treadmill crane.
The kataparuto tech rework, make their trebs walk 33% faster to keep up with infantry, similar to the Drill of mongols.
Their sniping potential is too strong, especially enemy castles get wrecked in seconds, lower their packing and unpacking to 33% faster for consistency.
For trebs wars, increase their accuracy by 33%, what’s the point of trebbing faster if you miss.
Some quality of life changes is to have capped rams in castle age, like Cumans because fortified walls can be researched and a battering ram will never breakthrough. Rams with anything garissoned including skirmishers better it’s attack and speed.
Also let the Japanese unlock siege ram, like most infantry civilizations: aztecs, slavs, sicilians.
Unlock Heresy and once researched bring back original samurai death animation; More honorable to die than to switch sides.
If a full monastery too much, exchange with Faith or Fervor, their late game army composition is expendable (halbs and champions, even samurai) to be converted.
Heresy is too pricey, reduce the cost to a third or more (330 gold) to appeal more to players.
Right now if you access the Japanese tech tree in-game steam version, Guilds are there.
Guilds for late game to sell floating food from fishing and buy other resources, historically Japanese had artisans and tradesman which involve guilds.
Wrapping things up, lose access Cavalier and add Hussar plus final plate boarding armor, late game food from fishing is always floating and spending on a scout-line rush would be the coup de grâce for the opponent.
The Cavalier serves no purpose in this civ, I tried sending cavalier to snipe enemy siege and they all died without reaching them due to arrow-fire.