Kindaichi Shounen no Jikenbo: Hoshimitou Kanashimi no Fukushuuki

The idol at the height of the popularity got involved in a scandal scandal. Idol manager Tachibana Yufu was searching for the truth of it and was found dead. The police asserted Yufu's death as suicide, but there were two people who had suspicions in that.
One was former idol and Yufu's best friend Katsuragi Yo and another one Yufu's fiance Takuya Asagiri. The two of them decided to take revenge at a leisure facility "Hoshijima" where the stakeholders gathered, but there was a also present a grandson of Kaneda detective Kindaichi and his friends...

[From vndbreview]