Another interesting expression/idiom
偕老同穴（かいろうどうけつ）: Till Death Do Us Part (lit. Together Death Same Hole)
Kotobank quotes the Book of Odes which contains the poem:
While living, we may have to occupy different apartments;
But when dead, we shall share the same grave.
If you say that I am not sincere,
By the bright sun I swear that I am.
(Translation from ctext)
Apparently, in Japan, this expression is also used as the name for the sea sponge called a Venus’ Flower Basket. To quote Wikipedia:
In traditional Asian cultures, this particular sponge (in a dead, dry state) was given as a wedding gift because the sponge symbiotically houses two small shrimp, a male and a female, who live out their lives inside the sponge. They breed, and when their offspring are tiny, the offspring escape to find a Venus’ flower basket of their own. The shrimp inside the basket clean it and, in return, the basket provides food for the shrimp by trapping it in its tissues and then releasing wastes into the body of the sponge for the shrimp. It is also speculated that the bioluminescent light of bacteria harnessed by the sponge may attract other small organisms which the shrimp eat.
Source: Yoru no Mijikashi
When you walk down the Takase river from the intersection at Shijoukiyamachi – down that dark street into downtown – there’s a certain old 3-storey Western restaurant done up in wood. The trees running alongside the Takase river are bathed in the warm light from over there.
But, even in this normally warm scenery, there was something even warmer within. It had crossed the threshold to piping hot.
Having just pledged their eternal dues, the newly married till-death-do-us-part couple could be said to be the very article of heavensent flawlessness – and while he carried his princess in his arms, exchanging those full kisses for the camera to catch – they piped hotter than hot cross buns in that very state of matrimonial contentment – fearlessly piping to the point where the surrounding congregation were burnt black in their boots.