The top companies of Japan 225 Index are TSE:7203, TSE:8306, and TSE:6758 — they can boast market cap of 233.82 B JPY, 135.32 B JPY, and 120.44 B JPY accordingly.
The highest-priced instruments on Japan 225 Index are TSE:6273, TSE:6861, and TSE:9983 — they'll cost you 66,810.00 JPY, 65,680.00 JPY, and 48,470.00 JPY accordingly.
The champion of Japan 225 Index is TSE:5803 — it's gained 398.39% over the year.
The weakest component of Japan 225 Index is TSE:6920 — it's lost −44.47% over the year.
Japan 225 Index is just a number that lets you track performance of the instruments comprising the index, so you can't invest in it directly. But you can buy Japan 225 Index futures or funds or invest in its components.