N2 — outside your level filter
write + (past) + now that
kaita ueha
now that; given that — a settled fact demands a resolve, stated in formal or declamatory register
こうなった上は、最後まで戦うしかない。
kou natta ue wa, saigo made tatakau shika nai.
Now that things have come to this, there's nothing to do but fight it out to the end. neutral
一度お引き受けした上は、途中で投げ出すわけにはまいりません。
ichido o hikiuke shita ue wa, tochuu de nagedasu wake ni wa mairimasen.
Having accepted the task, I cannot possibly abandon it halfway. formal