There have always been these kinds of worries and threats. Sometimes, they are associated with cults. If it's a cult, there's no need to worry about it at all, but such things do exist. In any case, basically, you don't need to worry about it, and you don't need to think about it. The idea that the number of souls decreases is just one possibility, and even in that case, there are several complex patterns.

・If there is a physical body, the soul is basically protected. The physical body acts as a defense.
・There is a pattern where souls merge. After death, the group soul, which is responsible for one's life, decides whether to end the soul as a separate entity and merge it back into the group soul. In this case, it may seem like the number of souls has decreased, but in reality, it is integrated into the group soul, and although the form has changed, it does not disappear. In this case, the number of souls decreases. It's more like merging into a collective consciousness than disappearing as an individual. Although it feels strange to say it disappears, it can be considered a disappearance from the perspective of an individual.
・The complete disappearance of a soul is also possible, but it is generally not the case. If the group soul decides that the life of a soul created by the group soul has failed and become so tainted that it is beyond redemption, it may perform a purification ritual to destroy the soul (completely), but this is a rare case. Even in this case, the complete disappearance of the soul is a rare occurrence. It is more common to cut off and purify only a part of it, the tainted part. This is the disappearance of a part of the aura, in the sense of purifying dirt and impurities. This is the same as everyday life. If your skin gets dirty, you wash it. It's the same thing. Discard the dirty part of the aura, purify it with fire (destroy it). This is something that is normally happening everywhere. Some sects perform fire rituals. It's the same thing.
・It is normal for souls on Earth to be reduced and moved to another dimension or another planet. The disappearance of souls is just an appearance, and in reality, it is a relocation. There are cases where no disaster occurs during this process, and cases where a major disaster occurs.

However, even if you know these things, there is no need to panic, feel a sense of crisis, or be manipulated or driven to take action based on a misguided sense of justice. The important thing is simple: keep your mind calm, calm your mind, and live a happy life.