On March 6, JR East released details regarding the incident involving the coupling detachment between the Tohoku Shinkansen "Hayabusa/Komachi 21" train. The company expressed its deep apologies for the inconvenience and concern caused to passengers.
At approximately 11:30 AM on March 6, while traveling between Ueno and Omiya, the coupling between the "Hayabusa" and "Komachi" trains (between cars 10 and 11) detached. This triggered the automatic braking system, causing the train to come to a stop around 6.6 kilometers from Tokyo. The "Hayabusa 21" was a 10-car H5 series train from JR Hokkaido, while the "Komachi 21" was a 7-car E6 series train from JR East, both operating in coupled service.
At the time of the incident, the train was traveling at about 60 km/h, with an 8-meter gap between the cars after stopping. Upon inspection, both trains were operated separately to Omiya Station, where passengers transferred to subsequent trains. Fortunately, there were no injuries, no derailment, and no damage or abnormalities found in the coupler. The coupling work for the previous train, the "Hayabusa/Komachi 10," at Morioka Station was carried out as usual.
Operations resumed at 2:34 PM across the entire Tohoku Shinkansen line. JR East announced that all coupled operations would be suspended until the cause was identified and necessary measures were implemented. The company also assured swift investigation and countermeasures. Due to the incident, on March 6 and 7, the Yamagata Shinkansen operated turning-back services between Fukushima and Yamagata/Shinjo, and the Akita Shinkansen operated turning-back services between Morioka and Akita, with direct services to the Tohoku Shinkansen canceled. However, the Yamagata Shinkansen "Tsubasa 121 and 160" continued operating direct services between Tokyo and Shinjo.
