Detective Galileo Series - Explosion

At 20:16 on October 13, on the surface of Longren Lake in Limu County, a small boat was overturned by a sudden explosion, and the red flames on the lake burned like a fire dragon.
Today is November 23, 11:06, Ota Ward No. 2 Junior High School's cultural festival, inland sea and bow cutting were sent to the school for a sudden state exercise, but no one came to see. When the bored duo was wandering around the campus, Inland Sea inadvertently found a plaster work, which was not as complete as a junior high school student, and when communicating with the bow officer, the teacher brought a woman to the classroom, the woman looked at the plaster line very shocked, and when asking the author, she accidentally learned that the plaster template was an aluminum plate found in the park, and the prototype of the plaster board was the son of a woman who had been missing for a long time.
After investigation, a body was found in the park provided by the author. In the research room, Inland Sea approached Yukawa with a plaster model and aluminum plate, and after telling him about the case, Yukawa was not interested in the case and was interested in how to make high-precision metal models on soft skin. However, Inoue said that the case had a lot to do with the university, because the deceased was a graduate of the university, majoring in the Department of Atomic Energy Engineering, and Kuribayashi was very panicked and changed the subject. Seisahiro Kijima, a professor at the time, Yukawa fell into contemplation after he finished speaking.
On November 26, Yukawa and Inland Sea came to the park to check the situation, where Inland Sea was explaining the intelligence that had been gathered, and Yukawa was looking around the park for something, which was a phone call, which was a report on some details of the deceased's autopsy.
The deceased, Yuichi Fujikawa, was exposed to radiation before his death, and after investigation, the founder of Fujikawa Company was Seisahiro Kijima, who was Yukawa's teacher before leaving school, and his research direction was related to atomic energy.
Kusanagi came to the Metropolitan Police Department and talked about the case that occurred on Longin Lake a month and a half ago, and after investigation, it was found that the body in the case also had radiation, but the identity of the deceased could not be determined now, and there seemed to be some connection between the two cases.
Yukawa came to the park alone to investigate, met the owner of the garbage dump, and at the garbage dump Yukawa found the wire iron pipe material, and yukawa knew it after seeing the material fracture. In the laboratory, Yukawa experimentally reconstructed the production process of the plaster statue, and at the same time judged the time interval of the actual death of the deceased according to the conditions of production.
The identity of the deceased in the Longren lake case in Tochigi Prefecture has been confirmed through DNA comparison, and the deceased in both cases worked for a company founded by Seishiro Kijima, which is very suspicious.
Yukawa came to visit Kijima Seishiro's home, the two were worthy of being teachers and students, the tone of the speech was the same, after a conversation, Kijima invited Yukawa into the house to talk in detail...