English: Picture of kai-sen at Tokyo National Museum Image Archives.
Note: This ship is either a shinko-sen, kai-sen, or maran-sen. Shinko-sen were used for international trade, mainly with China (Ming and Qing Dynasty), while the Ryukyuan kai-sen were often second-hand shinko-sen, repurposed for local trade between Satsuma and Ryukyu once the armaments had been taken off. A shinko-sen could also be called To-sen, or ‘Chinese ship’, as they were predominantly used for international maritime trade between Naha, the capital port of the Ryukyu Kingdom, and Fujian (Fuzhou) in China. Between AD 1383 and around 1450, shinko-sen-type vessels were granted to the Kingdom by the Ming when Ryukyu became a tributary state. Another ship type, maran-sen were middle to small-sized wooden junks made by Ryukyuan merchants for domestic trade, mostly within the Ryukyu Kingdom. The Ryukyuan kai-sen and maran-sen share the same basic ship structure as the shinko-sen and they were used up to the 18th century for local trade by private merchants between Naha and Kagoshima, the capital of Satsuma Domain in the southern part of Kyusyu Island. The construction of maran-sen started in the early 18th century. Shinko-sen and kai-sen are the largest with their hulls as long as 34.8 m, and 9.7 m in the beam, while maran-sen vessels are much smaller with a maximum hull length of only 14.2 m and beam of 5.4 m.

According to Rintaro Ono et. al., the ship in the picture is a kai-sen.