Solo Units are support characters that can be called into battle to unleash a combo. Once they join, they can be assigned to any of the Pair Units, so you could have Juri with Mega Man X and Zero, for example. They are listed in the order in which they join.
| CHARACTER | JOIN |
| Bahn | Chapter 2 |
| Tron Bonne (with Servbot) | Chapter 3 |
| Vashyron | Chapter 5 |
| Lindow Amamiya | Chapter 7 |
| Neneko/Neito | Chapter 8 |
| Heihachi Mishima | Chapter 10 |
| Sanger Zonvolt | Chapter 12 |
| Valkyrie | Chapter 13 |
| Flynn Scifo | Chapter 14 |
| Devilot | Chapter 14 |
| Arthur | Chapter 15 |
| Lady | Chapter 15 |
| Batsu Ichimonji | Chapter 16 |
| Imca | Chapter 17 |
| Alisa Bosconovitch | Chapter 19 |
| Rikiya Busujima | Chapter 21 |
| Bruno Delinger | Chapter 22 |
| Ulala | Chapter 23 |
| Saya | Chapter 23 |
| Juri | Chapter 26 |
