DLC Wave 3: Released on 11/7/2019
New costumes (servants wear, summer attire, evening wear) have been released.
These can be worn by both the protagonist and their students. Costumes can be changed via your Journal in the Monastery.

First set
New attire (Glasses for the protagonist, House Loungewear) has been released.
House Loungewear is for the protagonist and for student characters. It can be changed into from your Personal Quarters and will only be displayed in battle for certain classes. The classes for which the attire will be displayed in battle change depending on the character. Additionally, the attire change will not display for characters sent out as travelers.
The Glasses for the protagonist are an accessory that can be combined with any other outfit. The accessory can be selected from your Personal Quarters. If equipped, Glasses will be displayed on your player character at the monastery and in battle.

More details on the official game page of New Attire ...