Go to the mountain and into the tunnel of the newly opened road (from quest 20 completion).
Kill 5 spiders.
Quest 22
Go to the mountain.
Collect mushroom from grassy area.
Go to the shopping street and talk to chef (green haired man), on the southwest corner.
Quest 23
Go to the forest.
Collect 5 red slimy thingies.
Go to Residential street and talk to the kid (pale green haired) near the playground north entrance.
Quest 24
Go to the school's laboratory (2nd floor - Northeast room) and talk to the blue haired woman (new NPC).
Go to the shopping street, enter the weapons shop and you'll see a new NPC there, talk to him.
Quest 25 (to obtain it, you have to masturbate in school 5 times)
Go talk to the dark blue haired kid near the entrance of the school's bathhouse. (scene occurs)
After the scene the quest is complete and you'll unlock quest 45 later on.
Quest 26
Go to the slums area.
Talk to obscure merchant to the northeast corner.
Go to the mountains and gather a mushroom, sparkling rock and in the end a small red flower (the items are scattered along the path up until you reach the grassy area).
Bring the items back to the merchant and pick the 1st option.
Quest 27
Go and talk to the guy just outside the western inn.
Go to the riverbanks and follow the road to where you fought the werewolf boss, pick the orange flower.
You will have to fight.
After that go to the eastern part of town and talk to a girl close to the station.
Go and talk to the first guy again.