Sarunashi - saru猿 "monkey" and nashi梨 "pear" - is the fruit of some Japanese vine. It is rare to find it because it has a short shelf-life. In some areas of Honshu and in Hokkaido, it is more likely to be called kokuwa コクワ. Or in hiragana, as in the photo below.
The seed pattern in the section is similar to the kiwi fruit. It is called "hardy kiwi" in English.
The fruit has the size of an olive.
The wood of this vine is very hard. There is a famous bridge in Tokushima-ken made of it.