Don't Call It Mystery S01E12 - Final episode (Episode 2.5 sequel)

After seeing the art exhibition, Totonou Kuno (Masaki Suda) boarded the Shinkansen returning to Tokyo. When I was about to eat his lunch, Megumi Seki sat next to him. Somehow embarrassing, he eats lunch and goes to bed early.
When she woke up from a nap and suddenly looked at her seat next to her, Hiroko was reading a letter. When I saw her stationery, I instinctively said, 'Nah, go, ni, haku, ru, na.' Sei apologizes to the surprised Hiroko. But she doesn't make sense to Hiroko because she doesn't say that in her letter. She teaches that Sei is not a sentence, but a rearrangement of the initials of the illustration. Then Hiroko showed the other letters in order.
Hiroko tells her that her letter is from her father. Hiroko, who lost her parents at an early age, was taken care of by her late mother's best friend. But recently, Hiroko finds her old letter hidden in her mother's closet, which she raised. That is the letter she was reading that her father addressed to her mother now. She had heard from her mother that her parents had died, but her father's letter asked her to return her Hiroko. At her address in her letter, she got her reply when Hiroko wrote her letter. Hiroko, who is about to get married, asks her father to walk along Virgin Road, and she says she's heading there.
However, the illustrations in her letter are filled with dangerous messages. There was a person who gradually moved from one seat to another while watching the situation of these two people. When he finally reaches the back seat, Sei calls out. It was a woman named Saki (Atsuko Takahata).
Around that time, Inudogaji (Eita Nagayama) and others helped Seiko Furo (Sari Ito) and others, and heard the truth about the death of Aiju (Mai Shiraishi) from Hiromasu Tsuji (Takumi Kitamura). However, there is a new mystery ...