The Party Battle System is a unique feature introduced in the DS version of Mega Man Battle Network 5. Using this system, outside of storyline events, MegaMan can battle alongside the image data of up to 2 of his teammates, and even unleash certain combination attacks.
When the Party Battle System is first introduced, only the leading Navi of the player's selected version (ProtoMan.EXE or Colonel.EXE) can be added to the party. As the player continues to liberate Nebula-controlled areas during the storyline, the newest teammate gets added to the party. After the liberation of Oran Area 3, a warp appears in Lan's HP which leads him to a machine where MegaMan can change his party or restore deleted image data.
From this point onwards, during a Liberation Mission, if multiple team members are occupying the same tile, and a Liberate command is issued, the player can also choose to use the Party Battle System for that one Liberation attempt, using up to two team members. This comes at the cost of using up all participants' actions simultaneously.
In-battle, the player can choose to switch between Navis any time while accessing the Custom Screen or while fighting the viruses. This is done by touching the Navi using the Touch Screen of the DS, or via the X and Y buttons. Normally, the player can only change Navis up to 3 times, but certain Navi Customizer programs exist to increase the changes to a maximum of 5.
Each party member has their own set of HP, their own unique Charge Shot, and their own special chip. If a party member's HP is reduced to 0, an automatic switch is performed back to MegaMan, and the deleted party member can no longer be selected nor participate in further battles until the image data is restored at the party customization machine. If MegaMan is deleted while other party members are present, however, a game over will be issued.
The party members' base max HP, Charge Shot damage, and damage from support abilities remain fixed regardless of how strong MegaMan is. However, as Liberation Missions are completed, each of these values increases slightly.
Note that if MegaMan is in a Soul and a Navi Change is performed, the Soul is cancelled.
Party members also receive a reduced version of the Navi Customizer. Instead of a grid, the Party Customizer offers a series of slots in a row to accommodate Party Customizer programs. Only one rule exists for the Party Customizer - no two programs of the same colour must be touching each other. Different Navis have different Customizer capacities - often with non-combat oriented Navis like NumberMan.EXE and Meddy.EXE receiving the largest customization capacity.
Party Customizer programs are often prefixed with "P." to differentiate from MegaMan's NaviCust programs. The only programs for the Party Customizer that exist are as follows:
- P. HP +X (Raises max HP)
- P. Atk +X (Raises Buster and Charge Shot strength)
- P. Chip +X (Raises damage done by Special Chip)
- P. Battle Pack (Combines effects of the above 3 programs)
- P. Support (Allows party member to use support abilities)
Introduced alongside the Party Battle System are Support programs. These are compact programs that take up one slot in the Customizers for either MegaMan or his party members that allow them to perform special moves when not actively selected in-battle. The Support abilities are as follows:
- MegaMan: During battle, he sometimes appears and attacks with Cannons, Long Swords, or Mini Bombs.
- ProtoMan: At the start of each turn, he appears and performs a Wide Sword attack on the nearest enemy.
- Colonel: At the start of each turn, he appears and performs his Colonel Cannon attack.
- MagnetMan: When the current Navi is low on HP, MagnetMan generates a barrier to protect that Navi.
- KnightMan: When the current Navi would get hit from an attack, KnightMan may switch places with the Navi and take the damage instead. This continues until KnightMan's HP reaches 1.
- GyroMan: For the first two turns, GyroMan twirls his propeller, creating a Fan effect that draws all enemies to the front of the area.
- ShadowMan: When the current Navi is low on HP, ShadowMan performs a jutsu that damages and confuses all enemies on the battlefield.
- NapalmMan: During battle, he sometimes appears and fires vulcan shots at the enemy.
- TomahawkMan: During battle, he sometimes appears and performs his Tomahawk Swing.
- SearchMan: At the start of each turn, if the enemy has a chip loaded, SearchMan locks on to the enemy and fires, damaging the enemy and destroying their chip. This ability can even break the invisible AreaGrabs carried by Katana viruses.
- NumberMan: While loading two attack chips of the same code, after the first is used, NumberMan may freeze time and throw a die. The next attack chip will have its power increased by the die roll result x 10.
- Meddy: Each time the Custom Screen is opened, Meddy restores 5% of the current Navi's max HP.
- ToadMan: Once per battle, when the current Navi would be deleted, ToadMan revives the Navi with 230 HP.
When the current Navi is in Full Synchro, switching Navis will allow for a combination attack to be executed. However, not all Navis will perform a combination attack with any other. Combination attacks gradually grow stronger as the player completes more of the game.
A list of combinations are as follows:
|Navis Involved||Attack Name||Max Atk||Attack Description|
|MegaMan + ProtoMan||D-HERO|
|40||Much like the Program Advance of the same name, MegaMan and Protoman attack the entire enemy area with Buster shots and slash attacks, hitting around 10 times.|
|ProtoMan + MagnetMan||M-ZAN|
|240||Magnetman performs Magnet Hold on all enemies, before Protoman moves up and slashes each one. Each slash covers a WideSword range, so enemies side-by-side with each other take multiple hits.|
|MagnetMan + GyroMan||M-AIR|
|200||MagnetMan and GyroMan charge their Busters. GyroMan then transforms and drops Magnet Balls on the entire enemy area. Inflicts elec damage.|
|MegaMan + NapalmMan||D-VALCAN|
|20||MegaMan and NapalmMan fire a total of 18 Vulcan shots down the row. Hits behind point of impact.|
|MegaMan + SearchMan||C-SCOPE|
|40||A crosshair appears, centred 3 panels away from the Navi's current location. It then alternates between the rows above and below in a X-shaped formation. Pressing A stops the crosshair, and both Navis fire at that panel(s), hitting 5 times and piercing Invis. Locking on the corners of the X allows this attack to hit 2 panels instead of 1.|
|NapalmMan + Meddy||C-BOMB|
|150||Meddy generates a Chemical Flash capsule 3 panels away from the Navi's current location. NapalmMan performs a fire-element Napalm Bomb centred one panel behind that. Both bombs hit the 8 surrounding panels on detonation, and the central panels for each detonation must be vacant.|
|MegaMan + Colonel||BR-RUSH|
(Blind Rain Rush)
|100||Colonel throws his cape at one enemy. Both Navis then rush at that enemy, hitting it 3 times before finishing with a slash.|
|MegaMan + KnightMan||B-SHOOT|
|120||KnightMan jumps, causing rocks to fall. MegaMan then fires his Buster such that the rocks slide across each row. A total of 2 rocks cover each row, each one doing breaking damage.|
|Colonel + ShadowMan||E-SAPPOU|
|150||Colonel generates Rock Cubes in every possible panel adjacent to each enemy. ShadowMan then appears out of each Rock Cube and hits the 8 panels surrounding each one.|
|KnightMan + TomahawkMan||K-THROW|
|400||TomahawkMan throws KnightMan 3 squares away. He inflicts Breaking damage on the point of impact, and cracks all 8 surrounding panels along with the panel he lands on.|
|MegaMan + NumberMan||K-BOMB|
|100||MegaMan and NumberMan throw bombs into the air. They become 2x2 eraser blocks that cover the 3x3 area centred 3 squares away. An enemy in the centre of that area is hit 4 times, adjacent ones are hit a total of twice, and those in the corners hit only once. Affected enemies are confused.|
|ShadowMan + ToadMan||G-OTOSHI|
|60||A number of frogs fall on random panels, dealing water damage and turning panels they fall onto into Sea Panels.|