Meaning

‘Moto’ is used in the same way as the prefix ‘ex-‘ is in English. ‘kanojo’ (girlfriend) and ‘kareshi’ (boyfriend) are shortened to ‘kano’ and ‘kare’.

Example

別れてから半年がたつのに、まだ元カノのことが忘れられない。
wakaretekara hantoshi ga tatsu no ni, mada motokano no koto ga wasurerarenai.

We split up 6 months ago, but I can’t get over my ex-girlfriend.