Anyways why some character units like Marco, Fio, Eri, and Ralf has an illustration when its unlocked but not the following below?
Here's the only character units that has no illustration.
Trevor - Only in Another Story.
Nadia (Regular) - Only Special, Valentines, and Everlasting Summer versions of Nadia has an illustration.
Walter Ryan - Artwork only seen in Boy Memories Extra Ops.
Roberto Nicola - His character illustration is seen in the another story mode.
Abul Abbas - Only seen in the Another Story Mode and Special Ops.
Allen O'Neil - Only seen in the Another Story Mode and Special Ops.
Donald Morden (Except the Di'Cokka variant) - Only seen in the Another Story Mode and Special Ops.
Amadeus/Doctor - Only seen in the Another Story Mode.