In 1998, LSND experiment claims that they observed the unexpected excess of the anti electron neutrino events in their data. The data indicated the neutrinos which is sensitive to only gravity, so called "sterile neutrinos". Since then, there have been many experiments to prove or refute the existence of the neutrinos, but there are no conclusions yet.

In this colloquium, status of the "sterile neutrino" anomaly searches is shown including many planned experiments to search the neutrinos. One of the planned experiments will be held at J-PARC (JSNS2 experiment) in Japan soon, so the status of the experiment is also described.