Ivan Strugatskaya (イワン・ストルガツカヤ) is Kudryavka's grandfather and Chernushka's father.

Ivan Strugatskaya was born in Kalingrad, Russia. He got a job for a Russian space agency Glavcosmos; for which he had to move to Tebwa, a former colony of the Soviet Union located in the pacific ocean which is developing it's own space program. Later he got a job which required him to travel all around the world; staying a few months to 2 years in every country.

He loves Japanese culture; because of this he married a Japanese wife and got a daughter, Chernushka and taught her Japanese culture and language. When Chernushka got a daughter, Kudryavka, she was to busy becoming a cosmonaut on Tebwa to raise Kudryavka; so she let her father take care of her. Ivan took Kudryavka with him around the world, making her live in many different countries for a short time. He also taught her Japanese culture and language.

(Source: Little Busters! Wikia)