Meaning of “KidokuThrough(既読スルー)”

“KidokuThrough(既読スルー)” means “not responding after reading a message (especially on LINE)”.
“Kidoku(既読)” means “already read”, and “Through(スルー)” means “not responding” in this case.

LINE is the most popular message app in Japan, like WhatsApp, and on LINE, we can check read status.
It’s useful but sometimes annoying, because some people feel uncomfortable if someone don’t reply even though the someone check the message.

So, basically, I don’t open the message on LINE when I can’t reply soon to avoid “KidokuThrough(既読スルー)” situation. (If I open the message on LINE, sender of the message can know I’ve already checked the message.)

Example Conversation

A: I sent a message to Rica yesterday, but she is doing “KidokuThrough(既読スルー)”.
B: Why?
A: I don’t know, maybe I did something to make her angry…?

A: 昨日リカにメッセージ送ったんだけど、既読スルーされてる
B: え、なんで？
A: わかんない、なんか怒らせるようなことしたのかも？