Apparently not many noticed, but the unit that could be the Japanese Springald Ship, instead of the espingarda, launches arrows tied to a rocket. These were called Bo-Hiyas, and were launched with Yumi bows from boats. They were used for sieges and as an offensive method in marine combat, since they set enemy ships on fire with great versatility.
Wako pirates in a fune attacking korean villagers 1380_Author Wayne Reynolds
Bo-hiya for arrow shooting, Huolongjing
On the other hand, the Japanese are using ships based on Chinese Junkos, which means that they are using the Japanese version of ships they had in the Heian, Kamakura and Ashikaga periods. In the trailer only the arrow ship (1 flag) and Bo-Hiyas’ ship are shown replacing Springald’s ship (2 flags). The Warship is missing (3-4 flags).
The ships from the Sengoku Era of Aoe3 are not present. Maybe they put them in but in the Imperial age as a substitute for the Carraca or Warship, or with some mechanics that we don’t know.
Finally, some images of the Atakabune and the Tekkousen from Aoe3, which we hope some are the Japanese version of Warship:
Atakabune - AoE3:AD - Possible Japanese AoE4 Warship?
Tekkousen - AoE3:AD - Possible Japanese AoE4 Warship?