I feel this involves multiple killers, but I have not solved the first murder yet though that small stone seems to have something to do with the trick...
Thank you Irregular Scans for popping out the conclusion (3 chs.!) in one go!
Definitely a sad case and I must emphasize the importance of communication. :<
Now that I know about the spare key, I see how the suspect created the locked room scenario, but that still narrows the perpetrator to two suspects. Given that the scanlators did not translate the text on the floppy disks, I thought we had enough information as is, but I am stumped!
Usually in these kind of conversations, the one who starts bad-mouthing (in this case, the mother who even steered the conversation back to bad-mouthing the uncle when Kurogi-san tried to change the topic) would be the most suspicious, but can a SINGLE woman really sway everyone to talk shit...