As is advertised at the entrance with big kanji characters meaning 'We serve good mackerel', Sushi Daizen specialises in silver-skinned fish like mackerel, sardines and gizzard shad. Its location – a small space underneath elevated railway tracks with room for only nine seats – is a turn off for some, but it certainly adds to the atmosphere. You're also welcome to bring along your own drinks, which also goes a long way to creating atmosphere (a good place to stock up is at the liquor store on the second floor of Bic Camera outside Yurakucho Station). The staff don't speak English, but the chef, who's in his seventies, and his son and daughter run the place with that cosy family feel. They only offer set meals and the basic structure is sashimi, a grilled dish, nigiri and miso soup. They sometimes serve oysters depending on the season. As for mackerel, their specialty, they often serve two types with different origins, both as sashimi, so that you can experience the difference in taste. As the freshness of the seafood is their top priority, they only serve freshly caught fish – which means the restaurant is sometimes closed on Wednesdays, and all Saturdays, Sundays and public holidays, the same days Toyosu Fish Market is closed.