|Leaving your king sitting in its original location is asking for trouble.|
Masters of shogi have been sharing shogi wisdom through catchy sayings for longer than the rules of shogi have been written down. One of those popular sayings is, 居玉は避けよ or "Igyoku wa sakeyo." The translation is "Avoid a sitting king," or "A sitting king is a sitting duck!"
You don't want your king in shogi to hang out on its original square when the fighting begins. Typically, shogi games have very long openings compared to Western chess. The pieces you plan on attacking with are positioned, and the king is shuffled off into one of many possible castling arrangements for his protection.
No matter what castle you choose, make sure you get the king protected before the fighting begins. Even though shogi pieces tend to move slowly, the game changes pace quickly when the first pieces start getting captured. A silver general captured on the other side of the board can instantly drop behind enemy lines putting your king in danger.
Bishops and rooks also end up behind enemy lines without warning. You do not want your king caught out of his castle when one of these powerful pieces swoops in and promotes behind your lines!