Minus interest?

I'll write about Japanese stock market because I have nothing to write.

Yesterday's market is shaken between upward and downward because BOJ's president said about minus interest between bank and central bank.

I was with my mother and my little nephew, and watching ETF price when the president say that. Suddenly my revenue is increased. I knew that BOJ meeting held, and I recognized there was good surprise. I was pleasure my account was increased. But the revenue increasingly decrease. I think "oh, round trip market".

In the end, Tokyo market is closed upward.

*: I wrote "zero interest", but it's mistake. I knew "minus interest".