During the MER (Medical Emergency Response Team) operation in cities designated by the national government, the departure of Otowa (Kento Karai) caused the team to face unprecedented challenges.As the vacancy of the second doctor, Kitami (Suzuki Ryohei) feels a heavy responsibility, and the differences of opinion within the team also make the situation more complicated.

There are mixed opinions within the team on who should take Otowa's place.In particular, there were voices proposing to upgrade Hina (Ayami Nakajo), which made Hina feel even more pressured. She began to question whether she had the ability to succeed Otowa.However, Otowa firmly believed that Hinet should develop in the direction of circulatory surgery.

At this time, Aoto (Atsushi Ito) joined MER as a support doctor, bringing a glimmer of hope to the team.Aoto, like Otowa, was a medical technical officer at the Ministry of Health, Labor and Welfare.Ostensibly, he was sent as a replacement for the Second Doctor, but the motivation behind it may be much deeper than that.

Just as the MER members were trying to adapt to the new situation, a collision between a water bus and a houseboat occurred on the Sumida River.A large number of injured people required emergency treatment, but the Yakatabune lost control and the situation was extremely critical.Although members of MER rushed to the scene, they found that they could not approach Yakatabune directly.At the same time, they discovered a fuel leak at the bottom of the ship. There were too many wounded people on board, and there was a risk of explosion!

Faced with such a crisis, Kitami and others decided to adopt unconventional means for rescue.