Once the player frees him from captivity, he will follow them around, launching projectiles which home in on enemies, dealing considerable damage. The energy burst also inflicts damage to any enemy caught in its direction.
Unfortunately, if the player dies, he will stop following and run off screen. He also stops following when the player enters a new area of the mission.
Hyakutaro is a hidden boss found in Mission 18 (Pursuit). He fights by shooting slow homing energy balls from his palms. Once he's defeated, Hyakutaro gives the Iron Knuckle to the player and is added to the game's POW list. He is ranked as a Super Devil in this game, whereas other games has him as a 2nd Lieutenant.
Hyakutaro is a purchasable unit in this game. He attacks by kicking when in close range and shoots homing energy balls in long range. His special attack is firing five energy balls.
Hyakutaro returns in this game. Hyakutaro pieces can be earned through the POW Shop and the Normal/Extra Shop. Hyakutaro can now shoot ten energy blasts.
In both games, various entities of Hyakutaro exist, each one having their own ways of using their energy. It is unknown what relation (if any) they have to Hyakutaro.
Neo-Geo Battle Coliseum
During one of Marco Rossi's Supers he is able to summon Hyakutaro into battle. Once he arrives Hyakutaro will wander around until Marco makes contact with him after which he will charge a powerful energy blast at a random time after contact is made. This provides some unpredictable assaults upon the opponent. The blast is extremely powerful, and he can charge it as soon as he is provoked by the opponent.
- Hyakutaro possibly plays homage to Ryu from Street Fighter, as he uses a special attack similar to the Hadouken.
- It also resembles the energy projectiles seen in Akira Toriyama's Dragonball series.
- The energy burst seem from his palms also bears a resemblance to Andy Bogard's Hishouken, from The King of Fighters.
- His name is possibly a play on Hayato Ichimonji, the second main protagonist of the original Kamen Rider.
- There is an artwork in Metal Slug Anthology where he is a rebel in disguise using his signature attack.
- He was supposed to appear in Metal Slug Advance but for some reason it ended as unused. He still appears in a collectible card.
- "Hyaku" means "one hundred" in Japanese. Hyakutaro's variants in Metal Slug Defense and Metal Slug Attack are named after their download milestones.