Digraphia means the use of more than one writing system for the same language.
The standard examples are Hindustani and Turkish. With Hindustani there is at the same time an Urdu version written in the Urdu script, and a Hindi version written in Devanagari.
Japanese can use kanji, which is based on logograms, or hiragana or katakana, which are syllabic. The Romanization of Japanese also exists.