Let's talk about Exploration Base, one of the Denpa Island facilities today. It appears when you help an old man in Cave of Darkness 1 and it is actually quite a beneficial place!

This island lets you send Denpa Men to dungeons that you have already completed. They will come back to you 24 hours later with items and gold! The more Denpa Men you send, the more items and gold you can get, and the number of Denpa Men you can send increases up to 8 as you continue sending them to dungeons. You have a better chance of getting more items and gold if you send Denpa Men that have an advantage over monsters in each dungeon! For example, for Volcano you should try sending your red Denpa Men!

However, there are a few things you need be careful about! If your Denpa Men's levels are lower than the dungeon they are sent to, you will have less chance to get items and gold. Also, the Denpa Men sent do not gain XP. If there are Denpa Men you want to level up, you should choose other Denpa Men to send to the dungeons.