Source: Famitsu Three Houses guidebook (numerical data)

Credits: GFoppy (providing images of the guidebook)

Adjutants are helper/support units that you can assign to characters before a battle. They are similar to the support (rear) units in Awakening and Fates‘s Pair Up system. You can unlock the ability to assign Adjutants upon reaching Professor Level C or higher.

To assign an Adjutant, press the Y button in the deployment screen. Any character that’s not currently deployed can be selected as an Adjutant. At first, only 1 Adjutant can be assigned for your entire team. Upon reaching Professor Levels B and A, this limit will be increased by 1 each (for a maximum of 3).

While deployed, Adjutants gain 50% experience, the full amount of Skill Level experience (but no Authority experience) and Class Mastery experience, as well as support points. If the host unit falls in battle, the Adjutant will leave the battlefield completely unharmed.

Note: You can boost an Adjutant’s normal or Skill Level experience gain by equipping them with the Experience Gem or Knowledge Gem prior to battle.

Unlike the old Pair Up system, Adjutants cannot swap positions with the host unit mid-battle and they do not provide any stat boosts for the host unit. However, they do grant unique benefits depending on their role (as indicated by the icon next to their portrait).

Adjutant Follow-Up

Symbolised by a red sword icon. This is available for nearly every class.

Effect: Provides a fixed chance (based on the pair’s support level) of triggering an additional attack at the very end of combat. Can be triggered by attacking normally or by using Combat Arts; it doesn’t matter if the host unit misses. The Adjutant must be able to attack the enemy from the same attack range as the host unit.

Important: Adjutant Follow-Up attacks cannot trigger during the Enemy Phase.

Because of an oversight, if the pair have a C+, B+ or A+ support level, the activation rate will be 10%. This even applies for the protagonist’s hidden C+, B+ or A+ support levels (you can check via the “Share a Meal” or “Choir Practice” menus).

Update: The above issue appears to be fixed in Version 1.1.0.

The damage dealt via an Adjutant Follow Up attack will be equal to 50% of the damage if the Adjutant was fighting the enemy themselves. This includes any effective bonus from their weapon. But it does not factor in consecutive attacks (from a Brave weapon etc.). Certain Abilities that trigger during combat like Death Blow also do not apply.

Adjutant Follow-Up attacks can miss or trigger a critical hit. They do not consume weapon uses.

Adjutant Guard

Symbolised by a blue shield icon. This is available for: Brawler, Armored Knight, Grappler, Fortress Knight, Great Knight, Armored Lord and Emperor.

Effect: Always reduces the damage of enemy follow-up attacks by a fixed percentage (based on the pair’s support level). If an enemy follow-up attack would KO the host unit, the host unit survives with 1 HP instead (even if they are already at 1 HP). When an enemy triggers consecutive attacks, Adjutant Guard will not affect the 2nd attack, but will for the 3rd and 4th attacks.

Adjutant Heal

Symbolised by a green sparkling icon. This is available for Monk, Priest, Bishop and Holy Knight.

Effect: When the host unit has 50% or less HP, their HP is automatically restored at the start of your next turn. The amount of HP restored is the same as using the Heal spell. The number of times the host unit is healed depends on the pair’s support level.