'Convenience' also has 've' instead of 'bi', but that's not relevant. The loanword is コンビニ. When romanizing Japanese (or any other language) the etymology of a

'Convenience' also has 've' instead of 'bi', but that's not relevant. The loanword is コンビニ. When romanizing Japanese (or any other language) the etymology of a loanword has no influence on the romanized form (konbini).