Sirius Astronomical Observatory Murder Cases

Sirius Astronomical Observatory Murder Cases is a killing game and the first and final Duel Noir case featured in the first and seventh volume of Danganronpa Kirigiri.

The participants of the first Sirius Astronomical Observatory Murder Case are of the Detective Library, with Tadashi Asakura and Tōkichirō Endō acting as the Allurements of this case.

Volume 1
The Sirius Astronomical Observatory Murder Case is hosted by Tadashi Asakura and Tōkichirō Endō who are responsible for the murders that occurred inside the Sirius Astronomical Observatory. Tadashi first meets Tōkichirō in a park who tells him about the organization and then says that he will reveal to him the identity of the real criminal of the one who murdered his family under one condition. Tokichiro begins to tell him about Catharsis and, to get it, he must play a game called a Duel Noir, along the way telling him different rules. Having finished with all the rules, Tokichiro says that he cannot tell him who the criminal is, until he agrees to participate in the game and gives him one night to think it over and asks him to come to the park at ten o'clock in the morning. Tadashi accepts and says goodbye to the old man.

Five detectives are summoned to solve a case located on the Sirius Observatory who all first arrive at Hatesaki Station. Yui Samidare (DSC 888), Kyoko Kirigiri (DSC 919), Eigo Amino (DSC 367), "Shīta Enbi", and Kō Inuzuka (DSC 943)—were the detectives who were called to the case. The Detective group later arrived at the Sirius Astronomical Observatory and started to investigate the building and its furnishings. However, Yui along with the other detectives was tricked as the client never showed up, but instead, they ended up in another situation.

Later when Yui and Kyoko woke up, together they investigate the mystery surrounding the Observatory. The culprit, Tadashi is later revealed when he surrenders in front of Yui and Kyoko after the latter threatens to burn the building to the ground, to which they find him hiding in a small chair. Yui asks him who he is, to which he replies that his name is Tadashi Asakura. Tadashi confesses that he killed three people and lost, and later says that he sent an order on behalf of Ooe Yoshizono to five detectives to collect them in this place. He also adds that in Shita's letter, he indicated the time of gathering a little earlier to call him in advance before he killed, dismembered, and hid him in the telescopes and the chair, while he pretended all this time to be Shita and did not let anyone go to the telescopes. Tadashi was surprised that a novice detective like Kyoko was able to defeat him and asked her when she first noticed that the chair in which she sat, hid him, to which she says that this was part of her analysis from the very beginning.

Results and Aftermath

 * Yui Samidare and Kyoko Kirigiri become detective partners and eventually form a friendship.
 * Finishing the Observatory Case, another Duel Noir was about to be hosted at Norman's Hotel, discovered by outside means of directly messaging another registered detective through the DSC.
 * Tōkichirō Endō, although 'participated' indirectly, scouts and allures under orders to a parallel Duel Noir in Volume 7.