Contrary to every warning,
His whole empire cut brocades,
Half for wheel-guards, half for sails.
— Li Shangyin, Tang poet
The Tower Ship is the first heavy ship buildable by China and Japan, and is one of two heavy vessels that can be constructed in the Dark Age (the other being the Viking longship, usable by powers fronting the North Sea), sharing the same tactical stats with the Western Roundship, as well as its propensity for bombardment as well, with its multi-storey superstructure and rather large keel.
With this regard, China and Japan would easily win any naval fight if pitted against any European enemy but for one problem: Tower Ships, alongside their later upgrades, cost very little metal but have an increased cost in timber, meaning that to build a fleet, Asian armies would have to forgo the use of wood for their armies. Although for the Asians this may not seem to be a problem early on given their access to cheaper conscript infantry, this means that in the long run, especially at the onset of the Castle Age, the Asians will suffer problems with maintenance, especially if the cheaper and faster European war fleets can somehow cause sufficient damage to their economy. It is very difficult for China or Japan to bounce back navally once their impressive but costly fleet is destroyed. Still, having a warship capable of powerful long-range bombardment during the Dark Ages can sometimes translate into victory as long as your resources are husbanded carefully to obtain the right balance of terrestrial and maritime forces.
For centuries, naval combat in the Old World depended greatly upon boarding actions to pacify the crew and to take warships intact for one's own use. Just as in the West, the Chinese, Japanese and Koreans since the dawn of history built galleys with elevated superstructures, which allowed for the use of projectiles and artillery. Height was of vital importance, the higher you could build a ship, the farther out you could see at sea and the easier it was for you to resist boarding and kill off enemy crews with volleys of arrows. The tower ship was also mirrored in the Mediterranean, where during the early Roman era galleys were built larger and taller, resulting in the juggernaut "twenties" or "thirties", which disappeared and were later superseded by the galleass and the carrack in naval construction.