You might want some sort of warning for the player at first (you can apply a temporary no encounter state via a state or equipment, then force a battle) that she isn't strong enough to beat the enemies. Otherwise, the player might think they are supposed to fight.
It looks like the chest before the boss cannot be reached? Might frustrate some players.
The boss just kind of stands there while you think... The fight was kind of annoying with the silence and poison spamming. Poison does wear off after a while, but still annoying to deal with.
Also, you can't seem to do anything else (didn't check items), but you can guard while sleeping?
The fourth character's special is partially useless. It heals ailments, but Encore already does that? So it is really just a full heal for the party.
The optional boss's final text was kind of predictable. Not necessarily a bad thing, but...
The game was pretty short for me. Pretty close to that 20 minute mark.
This game gave me a bit of a SMT feel, though you can't capture enemies like you can in SMT.