Onion Cave

Floor 1
This is the first cave in Pikmin SP, and the start to your grand adventure. This dungeon has 2 floors, and 4 treasures. When you enter the first floor, you see 2 Snow Bulborbs in the middle of the passageway. Take them out, then move along the passage, killing any bulborbs you come across. As you walk along the tunnel, you find a circular room with a Red Bulborb in the center, a hole you can take to the next floor, 2 more Snow Bulborbs, and a treasure, the Slab of Justice. Carry that back, then be careful when attacking the snowy bulborbs. There is a chance that they may wake the Red Bulborb when they whine after death. Assuming you took care of the snowy bulborbs without waking the Red Bulborb, you can finally attack her. Defeat the bulborb to get another treasure, the Incredible Tart. Carry back that treasure, then, enter the hole to get to the next floor.

Floor 2
Here you arrive at the final floor. A Red Bulborb lies in wait near your ship's pod, so take it out before it has the chance to wreak havoc. When you're done with him, take the left passageway first, because the left has a nice surprise waiting for you. When you finally reach the end of the hall, you come upon a circular room with-you guessed it: Purple Pikmin. There are some candypops waiting for you there, 2 violets. The onion is there too, and another surprise: there is a treasure! Swap some reds for some purples, then grab the Truth Idol. Take it back, then go into the right passageway to fight your very first boss, the Dwarf Long Legs!

The First Boss Battle
This is the easiest boss battle in the game. Its attack happens when you throw pikmin to damage it. He will shake off your pikmin, then run around, hitting his head off the ground in an attempt to kill your pikmin. It is very easy to dodge this attack, you just have to get back into the passage until he stops rampaging. Repeat this process until he explodes and gives you a special treasure, the Metal Lover. This item will give you the Treasure Guage. After obtaining this, use the geyser to exit the cave.

After Onion Cave
When you enter the Onion Cave, it cannot be Day 1. You will most likely enter this cave on Day 2. Once you finish this dungeon, the day will end.

Poko Total
This cave has a total of 400 Pokos inside it.

Slab of Justice- 80 Pokos

Incredible Tart- 50 Pokos

Truth Idol- 70 Pokos

Metal Lover- 200 Pokos