その瞬間、私は現実感を失った。
Sono shunkan, watashi wa genjitsukan o ushinatta.
I lost my sense of reality at that moment.
瞬間 (shunkan: moment, second, instant) blink + interval
私 (watashi: I)
現実感 (genjitsukan: sense of reality)
reality (1st 2 chars.) + sense, feeling
失 (ushina(u): to lose)