さかのぼらなければならない【遡らなければならない】
sakanoboranakereba naranai
1. Must trace back; Must go back
★ Common
Adjective
#473609
1. Must trace back; Must go back
1. I see; that's right
1. mere; simple
1. to go upstream; to go up (a river)
2. to go back (to the past or origin); to date back (to)
1. National League
1. national chain
1. Becoming; After becoming
1. Became; Got
1. Become; Succeed