If your friend owes you that then it is your right to ask them to pay for it,
But I really doubt that your friend would pay you with Bitcoin maybe your friend would just pay you with Fiat ,
But with the price of what he/she borrowed .
No shy and no compromise with bitcoin and crypto currency so you are saying very right that it is too much long time period so remainder is needed for it, maybe he is not aware of it or maybe he forgot about it. So according to me bitcoin has become very high in price since 2016 and it is not good to hold peoples bitcoin for that long time, it is your right to remain him/ her about your bitcoin.