games.yahoo.co.jp is a 5 character word. It is a excellent domain length for people to type quickly.
Top Level Domain
games.yahoo.co.jp is still good but not best as same as .com. This is designed to target a specific country or audience. Remember that you can lose some web traffic to .com version of the domain because people tend to type .com more than any TLD.
a dictionary word. Excellent choice! Generally, people will remember dictionary words better than without.