By Wayne Chang, CNN Keelung, Taiwan (CNN) — You can now fall asleep on a ferry in Taiwan and wake up in Japan. On the surface, the Yaima Maru offers a perfect slow-travel escape — a passenger ferry equipped with saunas, karaoke rooms and a top-deck cafe. Launched in Taiwan last month to the sound of drums and a traditional lion dance, the 21,000-ton civilian vessel connects the northern Taiwan port of Keelung with the island of Ishigaki, in sout…