Tuesday's meeting between the South's President Moon Jae-in and the North's leader Kim Jong Un -- their third so far this year, but Moon's first trip to Pyongyang as president -- was no exception. 

Here are five things we have learned so far.

- Sister act -

Kim's younger sister Yo Jong, whom he sent to the South's Winter Olympics as his special envoy, has emerged as one of his closest advisers and is regularly seen at his side at public events. But she is developing a tendency to stray into shot.

At the first Panmunjom summit, she walked behind Moon and her brother, who were otherwise alone on the red carpet, until she suddenly peeled away. 

And again at Pyongyang airport she briefly joined them on a platform where they were to watch a welcome ceremony, before drifting into the cameras' vision several times as the two leaders and their wives made their way past well-wishers.

- Field of view -

All major South Korean television channels carried wall-to-wall coverage of Moon's arrival in Pyongyang, showing the airport events live and then switching to studio commentary and discussion until the next footage appeared. 

But the North's media is tightly controlled, even when reporting events in the country itself, and often eschews live broadcasts, preferring to show recorded footage. 

As Kim and Moon embraced on the tarmac the North's main state television channel showed only a test card, with eight unchanging vertical blocks of colour. 

- Disputed islands -

The unification flags waved by North Koreans at the airport showed a map of the peninsula, clearly including Dokdo, islands controlled by Seoul but claimed by Tokyo.

When similar flags were used ahead of the Winter Olympics in the South, Japan swiftly protested, and Seoul rapidly came up with an alternative version without the blue specks.

But Pyongyang is strongly nationalistic and constantly denounces Japan's 20th-century colonisation of the peninsula and its wartime atrocities.

A weekend commentary on the official KCNA news agency condemned Tokyo as a "political dwarf", adding that Pyongyang was "keenly watching Japan adding more crimes to the past ones and will have Japan pay dearly for them".

- Domestic bliss -

In their constitutions both North and South Korea claim sovereignty over the whole of the peninsula.

The Democratic People's Republic of Korea and Republic of Korea -- the North and South's official names -- were founded 70 years ago but each still technically regards the other as an illegal entity.

Relations between them are handled by Seoul's unification ministry and Pyongyang's Committee for the Peaceful Reunification of the Country, rather than their foreign ministries.

As such, a journey between them would not be regarded as an international flight.

And when Kim stepped onto the tarmac to welcome Moon, he emerged from a door marked "Domestic departure".

- Bait and switch -

Kim and Moon got into separate vehicles at Pyongyang airport before driving away.

But by the time the convoy arrived at the Paekhwawon State Guesthouse where Moon and his closest advisers are staying -- the name means "100 different flowers bloom" -- they were in the same open-topped car.

It later emerged that they had switched vehicles on the edge of the city and paraded together past thousands of citizens lined up along the streets.

"Reunification of the country!" the crowds chanted in unison, as the motorcade drove past the Kumsusan Palace where Kim's predecessors -- his father and grandfather -- lie in state.

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