PostgreSQL's unaccent function is unable to remove accents (diacritic signs) from Japanese characters like 'ド'

The postgresql out of box unaccent function is unable to remove accents (diacritic signs) with more then one diacritic in a character. The character 'ド' which is failing for normalisation have 2 diacritic signs in it. I tried to check the latest version ofhttps://github.com/postgres/postgres/blob/master/contrib/unaccent/unaccent.rules but still it does not have mapping for the Japanese characters like 'ド' . Can someone please guide how we can resolve this issue.