する verb
たいこうする
対向するバイクの存在を完璧に見落としていました。
I completely failed to see the oncoming motorcycle.
We are versus yonder (that side). We need to switch things around on that side, and we need to counter them now that it's our turn.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.