Let’s start this episode by introducing Minami Kamijou, Haruta’s elder sister. But she’s not here to say “Hi!” to her brother as Minami is very concerned…
…about his living conditions. You see, Minami Kamijou is an architect and seeing Haruta camping out is unforgivable that she wants him to go back home, something that Haruta doesn’t want to.
In any case, it’s time to find another apartment as the old place where Haruta stayed there will be demolished soon! Also, he can’t stay at Kusakabe-sensei’s house because of Chika-chan. I mean, she has a crush on that club advisor.
Anyways, they found an apartment that’s closer to school but it’s almost stuck in the middle of nowhere. While there’s a kitchen and bathroom, the apartment is soundproof so Haruta can play his trumpet whatever he wanted. But let’s get onto it as the Amano family are running this six-room apartment (or let’s just say five-room) after Kenji’s eccentric uncle passed away.
Unfortunately, he and his wife are going to sell the apartment as Mr. Amano is not rich to pay the inheritance tax. Also, there’s a rumor that there’s a ghost lurking around the apartment where they heard the priest staff ringing at night, which scared most of the tenant that they left the apartment after a few days.
But you know what, Haruta can solve this mystery but he needs help from his sister Minami as she’s an architect. It turns out that the apartment is constructed by applying “vernacular modernism”, meaning that Kenji’s uncle made the building based on his wacky ideas and its local surroundings.
See this giant key that Mr. Amano is holding? This is the answer to his uncle build this apartment in the first place.
Now all he needs to do is to find the keyhole…
And when Mr. Amano put the key into the hole and open it, a miracle happened on Christmas Eve! So, what’s going on here? It turns out that the apartment was also built as a secret piggy bank on a massive scale.
From having sound-proof walls to hearing the priest staff ringing during the night, it was built this way so that no one outside the building would hear 500-yen coins dropping down into the secret sixth room, which might tempt them to steel money from the Amano family.
But in any case, mystery solved and it looks like the owners of this apartment won’t have to worry about selling the building. Then again, Haruta won’t stay there unfortunately…
The Anime Rambler - By Benigmatica 
