Shining Resonance Refrain
47 Achievements
1,000
40-50h
Xbox One
Xbox Series
Know Others, Know Thyself
Acquired 100 different Traits.
30
5.78%
How to unlock the Know Others, Know Thyself achievement in Shining Resonance Refrain - Definitive Guide
The easiest way to unlock this achievement is to go on four dates with each of the characters (also allowing you to view each of their endings) and to always talk to them when they have the "..." speech bubbles. If you do, you should easily unlock this achievement as there are far more than 100 Traits.
Traits are different titles essentially that can be changed, and will give various bonuses based on who you are paired with in the Bond menu. Most traits will come automatically through the story, while some will be earned for equipping different costumes, doing night events and dates, or found in treasure chests. There are well over 100 in the game between all the characters, so I don't think a list is necessary (especially since like 70-80% are story related). Just be sure to go for all the endings and find every chest in each area and you should have no problem.