To Counter
する verb
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.
たいこうする
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
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.