There are 17 stats in the game:

Health
Intellect ("Mentality" in game)
Vigor ("Energy" in game)
Pride
Morality
Elegance
Character
Sensibility
Charm
Force ("Might" in game)
Magic
Stress
Height
Weight
SizeB
SizeW
SizeH

The stats that are used to determine the ending you get are in italic

Body condition:
if health < stress and stress >= 150:
sickness (Sick)
if vigor < stress and stress >= 150:
exhaust (Exhausted)
if stress > health * 0.5 or stress > vigor * 0.5:
tired (Tired)
if stress >= 100:
normal (Normal)
else:
Fine (Ordinary)

Mind condition:
if morality < 300 and ((morality + character) * 2 < (health + force) or (morality + elegance) * 2 < (health + force)):
juvenile (Delinquent)
if morality < 350 and (morality + character) * 2 < (vigor + pride):
arrogant (Arrogant)
if character + elegance < 300 and (character + elegance) * 2 < (vigor + health):
fuss (Fussy)
if gold < 500 and pride < (age - 10) * 60 + 150:
shabby (Grumbling)
else:
normal (Usual)

Body and mind condition only used for triggering certain events.

The initial stats and money are determined by your father's job.


Amount of stress added per turn are also determined by blood types.

A: stress +2.2/turn
B: stress +1.7/turn
O: stress +0/turn
AB: stress +2.7/turn

The last 5 stats are completely random from the start.
Height = 140.43 ~ 145.64 cm (+0.04 ~ 0.09 cm/turn)
Weight = 29.49 ~ 30.58 kg (+0.04 ~ 0.11 kg/turn)
SizeB = 68.13 ~ 70.72 cm (+0.1 ~ 0.27 cm/turn)
SizeW = 48.65 ~ 50.54 cm (+0.02 ~ 0.19 cm/turn)
SizeH = 68.65 ~ 71.96 cm (+0.15 ~ 0.26 cm/turn)

• Part-time jobs and studies are labeled as "Act"
  
• It seems that the dice roll influences amount of gold you get from part-time jobs and skill gain from studying (skill gain from part time jobs are not influenced by dice).
  
• Base skill/gold gain is directly multiplied by the dice roll (if you rolled a 6, you get 6 times the amount of skill/gold than if you rolled a 1).
  
• Only the first skill gain gets multiplied, the second skill gain does not.

TODO: Add list of jobs/studies.

There are 9 item categories (EquipCostume, EquipHelmet, EquipArmor, EquipWeapon, Own, Consume, DirectEat, Gold, PowerDice).

Own items gives bonus just by having it in the inventory (passive).
Equip items gives bonus when equipped (passive).
Consume items gives bonus when used, and is consumed upon use (active).
DirectEat items are automatically used when gained, acts like Consume items (active).
Consume and DirectEat items triggers consume event from their respective items' data.
Gold items are like DirectEat items, but gives gold instead of bonus and are handled differently.
PowerDice items are like Consume items, but said to influence dice number.
Consume, DirectEat, and PowerDice items do not have melee/magic defense.

Not only just clothes, all items have their own age restriction, but the age restrictions were never implemented in the game. You can wear any clothes at any age.
Also, all items have their status requirements, but unused. You can wear any clothes regardless of stats.

TODO: Extract and figure out information from game data.

Your max HP/MP is always equal to your health/magic stat.
maxHP = health
maxMP = magic

Your usable HP/MP is subtracted by half the amount of stress. This is called stress penalty (turns out, stress is deadly in this game).
curHP = max(1,maxHP - stress * 0.5)
curMP = max(1,maxMP - stress * 0.5)
NOTE: You can only declare battle to opponents if your stress is lower than twice your health, otherwise you won't be able to declare battle. If, instead, the opponent declares battle with you, you'll only have 1 HP in battle.
NOTE 2: You'll always start with at least 1 MP in battle, although it's possible to have 0 MP by starting with 10 MP and using a magic attack once.

First of all, the player with the greater roll attacks, and the other player defends. If both player rolls the same value, the attack is considered a miss.

Melee attacks are always possible. Attack Power is taken from force stat.
Magic attacks are only possible with at least 10 MP, and consumes 10 MP. Attack Power is taken from magic stat.
Item attacks are only possible with Cheap Clay Pot in the inventory. This consumes the item. Always causes 45 attack power.
Monster attack power are uniformly randomized from min/max range.
if attack is item:
. atkPwr = 45.
else:
. if attacker is human:
. . if attack is melee:
. . . atkPwr = force
. . else:
. . . atkPwr = magic
. else:
. . atkPwr = random(minMonAtk,maxMonAtk)

Attack damage is determined from this formula.
atkDmg = atkPwr * 0.5 * (1 + atkDice(1d6) * 0.11) + randomInt(0,10)

There is a 20% chance that a turn can do critical damage, and crits double the attack damage (not double the final damage).
if critTurn:
. atkDmg = 2 * atkDmg

Damage reduction is simply the sum of all your equipments' melee/magic defense (EquipCostume, EquipArmor, EquipHelmet, and EquipWeapon). If it's a monster, it uses their internal stats.
if defender is human:
. armor = sum of equipments' meleeDef/magicDef
else:
. armor = monMeleeDef/monMagicDef

Lastly, the attack damage is subtracted. The more armor or the higher rolls you have, the more damage reduction you'll get.
finalDmg = max(1,floor(atkDmg - (15 + armor) * 0.5 * (1 + defDice(1d6) * 0.12)))

Turns only pass when both dice number is not equal. Therefore, misses do not count as passing turn. Characters start talking at 5th and 8th turn.

After the 10th turn, if no one has died yet, the battle timeouts and the characters with the most HP% left wins.
NOTE: If both has the same %, left player wins.
leftRatio = leftCurHP / leftMaxHP
rightRatio = rightCurHP / rightMaxHP
if leftRatio < rightRatio:
. winner = right
else:
. winner = left

After fight, you gain might and magic. The amount of force/magic you gain is equal to how many times you attacked using melee/magic. If you used up all the 10 turns by doing 6 melee, 3 magic, and 1 item, you gain 6 force and 3 magic after battle.

Each character has 9 endings: The princess ending, the maid/bridesmaid ending, and other 7 endings based on stats. 9 endings times 4 characters equals to 36 endings.

Players are sorted from first to last by their prince's relationship points (literally called "prince points"). This determines the ranking of the player.
NOTE: There is no tie breaker for multiple players having same prince points, so if multiple players have the most prince points, depending on the sorting algorithm used, one of them becomes the princess (it would be funny if there's multiple princesses XD). The sorting algorithm is assumed to be not stable.
One quest cleared is worth 40 prince points, although some events can also give extra prince points. (see Quest)

You always get the maid/bridesmaid ending if you stand last, or the Princess ending if you stand first.
(Maid/bridesmaid ending is the worst ending, lol)

Otherwise, ending is only determined by whichever of these 8 stats is the highest:
Intellect, Morality, Elegance, Character, Sensibility, Charm, Force, Magic.

However, each character has one ending that are triggered by one of these two stats:
Maria (PM1): Intellect/Morality
Olive (PM2): Intellect/Sensibility
Risa (PM3): Elegance/Charm
Melody (PM4): Intellect/Morality

Depending on your father's job and your butler, the dialogue can be different.