Diseases are detrimental passive effects which can be seen in Rean's skill list. They also inflict Decay.
-Thin-Blooded: When wounded gain an extra rank. +1 Decay.
- Gained upon Starting game
-Weak: -3 ATK and +1 Decay per stack.
- Has a chance to gain a stack if you can't afford Rean's treatment.
-Drained: -10 Max HP and +1 Decay per stack.
- Has a chance to gain a stack if you can't afford Rean's treatment.
-Erectile Dysfunction: -1 Penis Size per Decay. +1 Decay.
- Has a chance to be gained if you can't afford Rean's treatment and he doesn't already have it.
-Weakened Immunities: -1 MDEF per Decay. +1 Decay.
- Has a chance to be gained if you can't afford Rean's treatment, he has 4 or more decay and doesn't already have it.
-Metastase: +3 Decay per stack
- Has a chance to gain a stack if you can't afford Rean't treatment, and he has 7 or more decay.
-Allergic Reaction: Poison: +100% poison gain. + 1 decay. If Rean has more than 10 stacks of poison at a time you automatically retreat and Rean gains Bedridden
- Has a chance to be gained if you can't afford Rean's treatment, he has 10 or more decay and doesn't already have it