Hallucination
noun
An illusion you have when you're awake is a hallucination.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
コウイチは時々、ポッドキャストをレコーディングしている時に幻覚を起こしてしまうんだ。
Koichi sometimes has hallucinations while recording podcasts.
この映像を見る時は、部屋を明るくしてはなれて見ないと、幻覚が見えてくるらしいよ。
When you watch this video, you have to watch in a well-lit place, not too close to the screen, otherwise I heard you'll have hallucinations.
フグは幻覚作用のあるキノコを食べたせいで、幻覚に襲われていたに違いない。
Fugu must have been hallucinating from the hallucinogenic mushrooms he ate.