Starting with Update 1.4, the Krobus is a potential candidate for resettlement to unmarried farmers. To learn more, read the guide on how to get a Krobus as a neighbor.
Krobus is in a sewerage system, which can be accessed with a Rusty key (it will be given by Gunther in exchange for 60 artifacts), using it on a hatch in the city or on the grid in the Syndersap forest.
Be lonely and ready to communicate
Keep in mind that you must be lonely – you can’t be married and make friends with Krobus. You can do this in several ways, but the easiest way is to give him the items he likes. The list below:
Diamonds
Iridium bar
Pumpkin.
Egg of the Void.
Mayonnaise of the Void
Wild horseradish.
The goal is to improve your relationship with the Krobus to 10 hearts.

Improve your home
Then you need to make sure you have a house big enough for the Crobus to move in. The size of the house you need is at least the first update you can buy from Robin. Price:
10,000 diamonds
450 trees.
Now we need to ask Krobus to move in with you as a friend. To do this, you will get a special subject called the Ghost Pendant of the Void.
Where can I get the Void Ghost Pendant?

Like the Mermaid’s Pendant, you can give this item to Krobus to move in with you. First, you need to achieve the maximum level of hearts in your relationship with the Mermaid. Then go to a trader in the Calico desert who will sell you a pendant for 200 Essences of emptiness. Give it to the Krobus and he will move in with you.
Krobus room

When the Krobus moves into your home, it will get its own room, which is a sewerage system. During the day, the Crobe hangs out in the house, and at night it will go to its sewer room. If you go back to the sewer instead of the Krobus, you will find a chest with a note that says you should leave the payment in the box. It contains all of the Krobus equipment that you can continue to buy.