The pairing is sometimes referred to as KikuWan, taken from Japan's human name and a portmanteau of the last syllable of Taiwan. The term, 菊と梅 (Kiku To Ume), Chrysanthemum and Plum, is also commonly used in the Japanese fandom, possibly referring to Japan's human name, (Kiku) meaning chrysanthemum, and one of Taiwan's human names, (Lin) meaning plum.
So far, Taiwan has not had any shown interaction in the webcomic with Japan, but an early illustration by Hidekaz Himaruya has her poking China on the cheek and telling him to leave Japan alone, which indicates that she prefers Japan over China (Though some fans think China is in love with Japan as well) and has led some fans to believe that she has a crush on Japan.
Due to their lack of canon interaction, fan interpretations of Japan and Taiwan's relationship are largely speculative, but it's generally assumed that China raised the other Asian nations as a family unit and that Japan and Taiwan hence likely grew up together, which would have given them time to interact with and potentially develop feelings for each other.
Since Japan historically colonized and ruled Taiwan from 1895 to 1945 with the intent of molding Taiwan into a showpiece "model colony", some fans assume that Taiwan lived with Japan during WWII before leaving and becoming the Republic of Taiwan.
In Chapter 42 of Hetalia: World Stars, Taiwan is shown giving chocolates to Japan on Valentine's Day.
Hetalia: World Stars
- Chapter 42: Valentine's Day in Japan
Webcomic: Extra Stories
- Doodles about Asia
- Ilha Formosa ~Beautiful Island~