Bowser Jr.'s Journey (Japanese name Koopa Jr. RPG) is a side story of Mario & Luigi: Bowser's Inside Story DX. Its gameplay is nearly identical to that of Minion Quest: The Search for Bowser.
The game opens with Kamek, Bowser, and Bowser Jr. finding out that all the Goombas in Bowser's Castle have gotten the blorbs. A small messenger bird shows up in Bowser's throne room and accidentally reports him of a meeting against the blorbs being held at Peach's castle. Angry that he wasn't invited, Bowser takes off for the Mushroom Kingdom with Kamek in his Clown Car. Meanwhile, Fawful sends a trio of his own minions, the Best Fitness Friends, to infiltrate Bowser's Castle.
Just like Minion Quest, Bowser Jr.'s Journey gameplay is dependent on building a squad capable of defeating an enemy troop. However, several noteable changes have been made.
- The maximum amount of troopers in a squad has increased from 8 to 9.
- A First Officer can be added to the squad. It must be Kamek or one of the Koopalings. Each First Officer has their own First Officer Skills that are similar to Captain Commands from the previous game.
- Depending on how you place your troopers, a formation buff can be granted to the squad.