Empty Bottles!
I. Go to Mist's house, and go look in the kitchen on the shelf. You will find an empty bottle.
II. Go to Jasper's house. Look through the boxes in the basement. You will find an empty bottle.
(P.S. You will also find a bottle of Rollabouti, which is important for a side-quest involving a bar owner...)
III. (This can be possible during the first spring, if you have a pet monster with a freindship of 3+ by 22 Spring. If not, you'll have to wait until the next year.)
Buy an egg from Nuemann before the day of the Egg Festival (23 Spring). On the day of the festival, give the egg to Jasper at the park. You will win the contest, getting 5000g and an empty bottle.
P.S.S. Empty bottles can be given to Edward the doctor if you have 3 medicinal herbs and 400g, and he will make you a potion that restores 150hp
More tricks, tips and cheats for this game are right here - Rune Factory: A Fantasy Harvest Moon cheats
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