In the Crescian society, on alternate Earth, the nobles take to settling disputes with mutual assassination.
The unspoken rule is that assassinations must be carried out directly by the nobles themselves. Should a noble be ‘caught’ in the assassination process, they will be executed, upping the stakes of the game. The preferred way to carry out this sport are indirect ways like poisoning, while direct bloodshed is frowned upon.
Due to how the Crescians have been poisoning and assassinating one another for centuries, they have developed an advanced understanding of chemistry and the biology of the human body. As such, not only has the field of poisoning advanced greatly, the law and crime investigations in the world are also quite developed. All existing Noble families train the Nobles in the skills of assassination, and take personal pride in conducting assassinations that the law cannot resolve.
Crescians Nobles are, by nature, very devious, but are very prideful and conscious of their honor, and their status as Nobles. Because of this, most Nobles adhere to the unspoken rule of personally carrying out assassinations, because if an agent is tasked with the assassination and is traced back to the Noble, the Noble and his family would be branded as cowards and suffer humiliation and a drop in status worse than death. Their entire family would also risk losing their Noble status.
A problem for this society is a general lack of mutual trust, as they're so used to mutual poisoning and assassinations. This lack of trust influences how nobles romantically court each other, as a lapse in judgement can lead to a painful death.
To solve this conundrum, the Crescians have created 'The Rite of Winter', which is a solemn ritual with implications in either spirituality, and/or in law, to be carried out whenever a couple decides to mutually start the courtship.
The Rite is to be carried out/renewed every period of time, and is effective for the next period, until either the time is up or the marriage, 'The Rite of Summer', is conducted.
My question is, what format should the Rite of Winter have, so that by completing it, the couple can have some sense of security and trust for the period of their courtship?
The more unlikely it is for the couple to betray one another, the better the answer. Also, it is important if the Rite can allow the couple to develop trust in one another, and/or explore their compatibility.
Note that we use Artistic License: Poisons, hand-waved by how the Crescians have been poisoning each other for centuries.
Tidbit: the reason for the name, Rite of Winter, is due to how the couple starts the relationship cold, and needs to warm up the relationship until it is warm/hot, leading to the Rite of Summer. The Rite of Fall can be seen as the divorce, and the Rite of Spring, is the name of the renewal ceremony for the Rite of Winter, with each renewal still being called the Rite of Spring.