Monkey Puncher Game Boy Color

At the start of the game, the player must choose to play as either Kenta (male) or Sumire (female). While the choice has little effect on gameplay, the sibling who is not chosen is the one kidnapped. Shortly after the beginning of the game, the player is given their first monkey, called Freddy, to train.

After obtaining the first monkey, and any subsequent new monkey, the player must befriend it by offering it food before they can begin training it. Over time, the monkey becomes more and more friendly towards the main character.

The monkeys are trained in skipping, using a punchbag, doing sit-ups, running and going shopping. These activities increase, respectively, the monkey's speed, power, strength, stamina and knowledge. In addition, a fifth option, sparring, has the potential to increase all statistics, albeit by a smaller amount.

In skipping, punching, sit-ups, and running, the monkeys learn to train by copying the actions of the main character whose motions are controlled by a rhythmic pressing of the "A" button. Over time, a monkey will learn to imitate these actions for a longer period eventually requiring no prompting for it to begin. The player can then choose to send the monkey out to shop for certain items or let it simply buy what it wants—this is the only way to obtain new items. As its knowledge increases, the monkey will be able to follow a shopping list with greater accuracy and bring home rarer items. Sparring involves a normal match between the player's monkey and a computer-controlled opponent, although without a clear winner or any reward beyond stat increases. All the monkey's stats have a maximum limit. It is possible to date your monkeys either with each other or with a monkey from a friend or a dating shop within the game. After dating, the first monkey vanishes and is replaced with a new baby monkey. The maximum stats for this new monkey may be higher or lower than the player's original monkey, depending on the monkey it is paired with. A monkey with all the stats maxed out will produce a baby monkey with much higher maximum stats.