A manga book published in 1999 randomly predicted a disaster in March 2011, which seemed to come true with Fukushima. The manga was re-published in 2021 predicting a M8.8 in July 2025, but nothing happened. This is the dumb prophecy part, it was not based on seismology studies, just a shot in the dark to try to seem prophetic again. Countless works of fiction are published every year which predict some future disaster at an arbitrary date. Every once in a while, one of those thousands of random predictions can be interpreted as coming true when something bad happens on that day, which retroactively drives interest in that work of fiction, and less scientific minds believing the author has actual future predicting power beyond the abilities of science.

A relatively major (but not M8.8) quake has now hit in December 2025. It is intelligent to expect there may be aftershocks in the days after a significant earthquake actually happens, which can sometimes be larger than the initial quake. This is a well-accepted scientific fact born out of large amounts of data and statistical patterns, not whimsical doomsdayism.

Fukushima's M9.0-9.1 was around a 1-in-1000-year scale event. The last time Japan saw such a powerful earthquake was in the 869 AD. It would be reasonable to expect one of that scale to not happen again for another 1000 years.

You asked what I would have asked, in a sentence, my understanding is: it was LITERALLY a prophecy, I.e. an unscientific statement out of thin air, that in July, there would be an earthquake followed by a larger one. Here, we have reality, an earthquake, ergo the first prong of a mega quake was satisfied, as opposed to prophesied.