Not a bad game. Took me quite a while to complete it though...
Game Mechanics:
When you H a girl, you temporarily learn her skill.
When you revert her into human form and H her, you would learn her skill permanently(Some may have limited uses)
Skills:
Cat girl: Sniff ability, lets you sniff up items in 2 blocks away.
Bat girl: Night vision
Mummy: Heals yourself( Permanent has up to 3 uses)
Knight(Berserk) : Deals double Physical damage next hit
Spider woman: Stalls enemy for 1 turn (Not effective on some enemies)
Mandragora girl(?): Stops enemy from using skills
Gargoyle girl: Suffers no damage, but unable to move
Dryad: heals yourself slightly, and opens blocked paths(by trees)
Banshee: Enemy do not detect you(If I am not wrong, use it before they appear, and they will not appear)
Mermaid: Breath underwater
Dancer: Charming dance (Never used it, not sure of actual effects)
Water priestess(?): Floods the underwater sewerage
Siren: Allows you to fly for 1 turn, allowing you to hover/move.
Succumbus: Allows you to go into someone's dream
Clam girl: Allows you to negate the next damage(Permanent up to 3 uses)
Fallen Angel: Divine punishment does major damage to enemies up to 2 squares ahead (Permanent up to 2 uses)
Minotaur: Dash in to attack. Consumes Stamina, but no turn used. (Requires confirmation: Next action too, will not end the turn. This means you can do 3 actions in a turn if the 1st action is this skill)
Kali: Allows you to do a second physical attack on your next physical attack (Permanent up to 2 uses)
Basilisk: Evil Eye that does damage while petrifying the enemy
Student Leader: Heals when you walk(?) Up to 3 uses in Permanent
Walkthrough(Very rough guide, own exploring required):
School:
Find shirt, defeat cat.
Defeat cat somehow in one turn (you may level up a few times, or get that dagger on the floor)
Bring her back and H her, you would then get the blue key.
Go to the second level, and you would enter a dark area. Avoid the bat girl for now. Use the map and locate a stairs.
A mummy would be seen later, feel free to avoid or engage combat. You would enter a second dark area later. When you get in, prepare to get out, as the bat girl would follow you into the light, where you can fight and learn her night vision. Get the fire scroll behind her. Using the night vision allows you to clear the first dark area, revealing doors that were not visible at first. One of the doors requires a copper key. The other door needs you to use the fire ball to light objects up to open paths. Behind the locked door, there is a sword behind a warp point. To access it, wait till the mummy is on the trap itself, then open it. She would fall, and the warp point would be gone temporarily.
The warp point that blocks the path to the arena is unlocked by engaging both switches on its sides, one requiring you to open the locked door.
Once you get down to the arena, run away, and walk along the walls until you see a point where you drop down. Following the path allows you to enter the garden. Remember to pick up the key to have a shortcut from now on.
Garden:
Use your fire to burn down spider webs.
Defeat the spider girl within 2 turns to learn her sticky web.
When the mandragora girl chases you from under the ground so as to prevent you from getting treasures, lure her such that you have access to the treasure, and use the sticky web to web her. Once you get the treasure, the mandragora girl will leave crying. One of these treasures is an Earth scroll, which allows you to dig up treasure(with the help of the nose) as well as the Mandragora girl. There is also a gargoyle girl, but she serves no big purpose. At the end you would find a Dryad that is rather hard to deal with. Make sure you picked up the different equipments on your way there, and that you have both the Mummy and Mandragora girls' skills. On your first turn, seal Dryad's heal up. Then attack, heal with Mummy's ability, and attack. You may want to use potions should there be a need. When you win, you cleared the area, and move back to the school, with a gold key for a shortcut.
Underground sewage:
Basically explore, and if you see circles on the map, you can use fire magic to light them up. Some may open new paths. One of the switches needs additional weight to open, if you want to open it, simply use Gargoyle girl's ability when standing on the switch. One switch is rusted, and needs you to use a lightning spell to engage it. On the south end you would find a switch that enables you to manipulate the water level. Mermaid gives you the ability to breathe underwater, and you need it to access the Ice scroll on level 2. Ice magic allows you to freeze 2 squares of water. Take note that you would slide on it, rather than walk. So if it exceeds 3 squares, you will fall. Having this spell, you can now use the east stairs (make sure water level is down). Light the torch and freeze the water. You would then enter into the Dragon's nest. You do not need to defeat the boss as of now, so it is really optional. However, be prepared to take a lot of damage. If you want to avoid her, you would still have to engage in combat with her MULTIPLE TIMES. This is simply because when she starts a battle, she uses flood. This would make you take damage and go out of breathe, taking an additional 10% of your HP off each turn. However, if you run away from battle now, you can swim across the pitfalls. Remember to use Q and E to choose the direction you escape towards. Getting past her lets you clear the sewage, and you move to the ancient ruins. A platinum key opens the shortcut this time round.
Ancient Ruins:
If you see a cup on the map, shoot a far ranged fireball at it, and doors will open. Siren's ability is not really needed now. Succumbus's ability is a must to get however. On the second part of the map, there is no direct path. However, you would see a sleeping clam girl. You need to use Succumbus's ability to enter her dreams, and you would notice some paths are opened/closed in the dream realm. Find your way across, and you would get to the boss, the Fallen Angel. The fallen angel has a charge attack that kills you in a single hit. To survive, you need the clam girl's ability to negate an attack once. Armed with good weapons, you should somehow be able to win this battle. You can then get the Last Key for shortcuts, as well as access to the tower.
Tower:
Kali is the most important girl in the area. You MUST defeat her in 2 turns. Doing so lets you learn her skill to attack twice. This means if you took 2 turns to defeat her, you only take 1 turn now! Basilisk may be a pain, so be careful, as she can do ranged attacks. There is a switch on the right of the map that lights up the dungeon as well as show your map. Some of the passageways have hidden paths, revealed by a button opposite to the door, or can only be opened when you drop from above. On the second level, you would find a minotaur, as well as warp points. Before that, if you missed Siren's skill, now is a good time to go back to get it. When you get onto the second level, you would find a pitfall on one end. If you use Siren's ability, you can fly past the hole and get the strongest weapon in the game! The warp points requires you to place the 4 crystals from the 4 areas to open the path to the final boss. To get the crystals, you need to revert the bosses to human form, and obtain their permanent skills.
The red crystal is found in the school, you need to defeat the berserk knight. Then go on one of the warp points in B1 to a door that needs mighty strength to open. The red crystal lies there.
The green crystal is easiest to find. From the school, using the shortcut, you would come to the exit of the garden. Simply walk ahead to the blocked path, and the green crystal lies there. There are no enemies other than the boss on the last map, so you can take your time exploring.
The blue crystal is found on the way to the boss's area(1st floor, go east stairs. Light torch, freeze path. Walk to the end, on the right.). You need the boss's skill to flood the area so you have enough time to reach the blue crystal.
The yellow crystal is in fact on the way along the shortcut. To defeat the fallen angel in 1 turn, simply use mighty strength(does twice physical damage) + double attack from Kali(does 2 attacks), allowing you to do 3x your normal damage. When equipped with the strongest weapon, you should have no big issues.
Finally, the boss is quite a pain. However, you might be interested to know that:
1) Once you use an item, he would set a curse that prevents you from using items
2) He would use the 1-hit KO divine punishment.
3) Basilisk's demon eye can petrify him!!
4) Mandragora girl's cry seems to work to prevent his spells. Not sure its true effectiveness though.
5) Naturally, it is quite common sensical to use negate damage+double physical damage+ double strike first, but he would not be killed that easily!
Well, that is all I can say. Remember to save when you finally win. If you need any further assistance, just ask around.
P.S. if you choose to protect this world, is there anything unlocked? There is no path to the final boss area, and nothing seems different... Is there any ending in that case?