Authorities in Japan are stepping up security measures following a series of incidents where detergents, sleeping pills, and other substances were found in students' tumblers at elementary schools.

According to the Japanese weekly magazine AERA, an elementary school in Suginami Ward, Tokyo, reported incidents in February and March 2024 where students spat out their drinks after noticing strange smells and tastes, such as detergent or soapy water.

In another incident last September at an elementary school in Adachi Ward, a student was caught putting a sleep-inducing drug into a classmate's tumbler.

Similar acts, including the insertion of rubbing alcohol or magnets, have been reported in various locations across the country.

In May, an elementary school teacher was even caught engaging in inappropriate behavior involving a student's tumbler.

As the situation grew serious, the Suginami Ward Board of Education ordered that tumblers be stored next to the teacher's desk instead of in lockers at the back of the classroom, and that students must carry them when moving between classrooms.

They also instructed that the police be notified immediately if there is any suspicion of foreign substances being introduced.

Tumblers equipped with anti-tampering features using fingerprint recognition technology have also emerged.

A fingerprint-locking tumbler released by a sports fashion company in Osaka has sold more than 10,000 units in six months.

The tumbler prevents the lid from opening for anyone other than the registered user, effectively blocking third-party access.

Originally developed to prevent drug tampering for athletes, it is now gaining attention as a must-have item among Japanese parents with elementary school children.

Experts have warned that while children under 14 are exempt from criminal punishment under Japanese law, their parents may still be held civilly liable, and those 14 or older could face charges for property damage or assault.

Reported by Jung Da-eun | Video by JISOO | Graphics by Yang Hye-min | Produced by SBS Digital News