A Wakizashi is a type of Japanese sword with a blade length between 30 and 60 centimeters (12 and 24 inches), similar to but shorter than a katana. The wakizashi is usually not a primary weapon for samurai and was often worn together with the katana. The pairing of a katana with a wakizashi is called the daishō.
The first usage of a wakizashi dates back to the period between 1332 and 1369. It handles with one hand only, the handle being generally sized to the width of a palm of hand. It can also be used as tools to decapitate defeated enemies and sometimes to commit seppuku for samurais. As the blades were relatively short, fighters had more control over his movements than when using a longer blade. During the Edo period (1603–1868), the Yakuza were permitted to carry a wakizashi, which has become generally their weapon of choice in melee.
The wakizashi is little more than a boosted combat knife, with the same AP, Strength requirement and range, for a little more damage. It's slightly weaker than the "Little Jesus". However, it does seem to be able to bypass the Damage Threshold of any armor, justifying the in-game description.