A portable cassette player (Cost: 100 Pink Trigger's Power)

The professor saw me eyeing the cassette player and regarded me curiously. "Ah, that is... an interesting and unfortunate piece of history, although it's certainly questionable if it can tell us anything about the Rokkenjima mysteries. As you'll recall, this was a new model back in 1986. It was actually put on order by Ushiromiya Krauss for his daughter, but, ah... He reserved it to receive it a month after October of that year, so... Ahem. Quite unfortunate."

Could that guy have any worse luck with investments? I felt sorry for him, as I often did. I said nothing, though, and let my mentor keep going.

"Now, this old thing may look like a dinosaur these days, but back then, this would have had all of Jessica's friends burning with envy. You see, at that time, a portable, personal music player was cutting-edge technology! Listening to your cassettes wherever you want, with the luxury of dual audio..."

Are you trying to sell it to me...? I coughed, a bit impatient for the Professor to wrap it up.

"Ah, yes... Well, that hardly means anything now. Naturally, there wasn't any kind of smoking-gun cassette inside it when I purchased it for the collection. There wasn't anything at all inside... Still, what's most interesting about this is the sentimental implications, don't you think? Most believe that Krauss brought up his daughter strictly, creating a friction between the two of them owing to the great expectations she had in consideration of the headship... This definitely wasn't cheap back in the day. I guess every father wants to see his daughter smile, hm hm."

... I was distracted, thinking of Jessica listening to the modern music of the time with a big smile on her face. Ah, now that I think about it... a device like this would have been a great way for humans to listen to music they didn't want others to hear. That's a rare situation, sure, but... If I was on Rokkenjima with music that day, maybe I could see unexpected sides of a number of different humans...

... I realized I'd said that out loud, and the professor was giving me a puzzled look. "Are you saying... such a device is tied to the mysteries somehow? Please, you have to elaborate!"

I sighed, trying to come up with some excuse. In the end, I... think I ended up saying something that made it sound like I was just daydreaming about the memory of Jessica, which was actually a shade less humiliating than where my mind had actually started going. The Professor sighed, then hurriedly thought of a reason for us to leave the room.