It is possible to beat the demo without submitting to any enemy. The "adventurer" class the MC has gives a single ability - defend. If you use this ability, you heal a small amount of health, slightly reduce the damage you take before your next turn, and you will block and counterattack against any enemy grapples until your next turn. The amorous slimes spend a turn telegraphing their grapple attack, giving you plenty of time to defend against it.