I bought a pack of Blu-ray blank discs at Yamada Denki for 1151 yen ($9.59 €7.99) to record TV shows. The pack includes 10 discs.
Most of the discs in the store are made in Taiwan. Only Panasonic discs are made in Japan. In the Internet, many customers recommend to use discs made in Japan, if you want to keep the data for a long time safely. So I chose Panasonic discs. The below is the link to Amazon.