Just for kicks and assuming that it's not Japanese at all, Google Translate says "niji" can mean:
Bosnian/Corsican/Serbian - Important
Chinese - Nicky
Greek - Allusion
Gujarati/Hindi/Urdu - Private
Igbo - Continued
Kannada - Manufactured eyeglasses (?!?!)
Malagasy/Xhosa - Fiji
Russian - Below
Yoruba - Nightmares
Take your pick!
Bosnian/Corsican/Serbian - Important
Chinese - Nicky
Greek - Allusion
Gujarati/Hindi/Urdu - Private
Igbo - Continued
Kannada - Manufactured eyeglasses (?!?!)
Malagasy/Xhosa - Fiji
Russian - Below
Yoruba - Nightmares
Take your pick!