Sui

 (スイ (スライム)) is a slime that Mukoda took as his second familiar. At the time when he got as a familiar, Sui was just a baby slime but on the 3rd day he evolved and 5th Volume a fugitive slime. Sui is the main character of the spin-off cartoon "Sui's Great Adventure".

History
Basically, as a slime Sui would eat anything, and when he had eaten another-world trash from the online supermarket, a contract between Mukoda and Sui was established. Sui also tasted Mukoda's food and is a gourmet of his dishes. Formerly, Sui can not speak words as a slime, but later obtained the ability to talk. Sui is a special individual and its normal size is a bowling ball and the color is light blue. Specializing in water magic, recovery medicine generation, it is a useful monster besides combat such as blacksmith, but it is beginning to be influenced by Fel, and it is becoming a battle junky. It is usually in Mukoda's bag and the youngest being in the party, including taste and behavior. Although there is a part where Sui can not read between the lines, he is well loved by Mukoda because Sui is a very honest and sweet-tempered character. Sui calls Mukoda "aruji", a term used by a servant to it's lord meaning master.