BBC Sport's Ask Me Anything team explains what sumo wrestling is, why they eat up to 10,000 calories a day and why the Grand Sumo Tournament is in London.
Sumo is the iconic national sport of Japan, but it is also a mix of tradition, discipline and Shinto religious rituals going back more than 1,000 years.
It is a combat sport with two wrestlers – called rikishi – fighting inside a raised circular ring – a dohyo – 4.55m (14.9 ft) large. Rituals and ceremonies are performed before and after each bout, highlighting the traditional nature of the sport.
Traditionally before a match, a hole is made in the centre of the dohyo and filled with nuts, squid, seaweed and sake by Shinto priests.
The hole is closed, enshrining inside a spirit. Sumo wrestlers then perform a ritual stamp and clap to scare away bad spirits.
Professional sumo is ruled by a rigid ranking system, and the wrestlers who participate dedicate their entire lives to it - living and training communally.
How does a sumo bout work?
The basic rules of sumo are quite simple. The bout is decided when a rikishiis forced out of the dohyoor touches the floor of the ring with anything other than the sole of his feet. Bouts can be over in a fraction of a second or last over two minutes.
There are two main fighting styles in sumo. Pusher-thrusters tend to shove their opponents out of the ring by force, while belt-fighters prefer to grapple the other rikishiand use judo-like throws.
High-ranking rikishioften excel in more than one type of combat and are able to adapt to their opponents.
There are 82 winning techniques, ranging from audacious throws to clever side-steps. The variety of techniques and strategies keeps fans fascinated, so surprises and upsets can happen in any bout.
There are no weight classes in sumo, so it is normal to see rikishiwith huge size differences. Sumo rankings determine who is fighting who, rather than physical attributes.
While women can and do compete in amateur sumo wrestling around the world, they cannot enter the ring at Tokyo's 11,000 Ryogoku Kokugikan arena, or compete in professional tournaments.
What is life like as a rikishi?
Sumo wrestlers live and train together in training stables called a heya, led by a stable master.
The daily life of a rikishiis dedicated entirely to sumo. They wake up early for an intense morning practice, followed by a rich lunch of chankonabe (a high-protein stew designed to build bulk), and an afternoon nap.
The average wrestler consumes between six to 10 bowls per meal – around 10,000 calories – although the retired wrestler Takamisugi became famous when he reportedly ate 65 bowls of chankonabe in one sitting.
Rikishiintentionally gain weight to maximise their leverage in the ring. Despite their massive size, they are incredibly flexible, agile, and have explosive power.
Almost every aspect of the rikishi'slives are regulated by their stable and the Sumo Association – making sumo lifestyle unlike any other professional sport.
A rikishi'sranking regulates whether he is paid, allowed to have his own room or even live outside the stable or have an assistant.
Younger or lower ranked rikishi cook and perform chores around the heya, while higher ranked ones enjoy other special privileges.
Sumo rankings are determined by each rikishi'sperformance in the six annual 15-day tournaments. Rikishi with a winning record, go up in the rankings, while those with a losing record go down.
Ahead of each tournament, a new banzukeis published, which is a single large sheet of traditional calligraphy containing the new ranking of all rikishi in professional sumo.
At the pinnacle of sumo there's the rank of Yokozuna – the grand champion. They are expected to embody the spirit of sumo - beyond being a champion in the ring.
Who are sumo wrestlers?
There are only around 600 rikishi in professional sumo and the majority are Japanese.
Foreign rikishihave featured prominently in the sport for decades, with Mongolian wrestlers dominating since the start of the century.
One of the two Yokozunacompeting today – Hoshoryu – is from Mongolia. There are also two rikishi competing in the top divisions from Ukraine, while previous high-rankers included wrestlers from Eastern Europe and the Pacific Islands.
Earlier this year, 15-year-old Nicholas Tarasenko from Hull went to Japan to train become a professional sumo wrestler.
How can I watch?
The Grand Sumo Tournament is taking place in London from Wedneday, 15 October until Sunday, 19 October and it will be live on BBC iPlayer and the BBC Sport app.
The action from the Royal Albert Hall gets under way at 19:30 BST as the competition takes place outside of Japan for just the second time.
Explaining why the competition has gone overseas, Hakkaku Rijicho, the Japan Sumo Association chair, said he wanted to "convey to the people of London the appeal of Sumo - an ancient traditional Japanese culture".
Sumo has seen a significant rise in popularity among international fans in recent years, and a rare international tournament abroad could further boost the appeal of Japanese culture abroad. Sumo is also set to visit Paris in 2026.
This article is the latest from BBC Sport's Ask Me Anything team.
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