Unsolsexual is a label on the asexual spectrum that means one is, for the most part asexual, but with the exception of exactly one person whom one can feel attraction towards. It's different from being monoamorous, as someone who is monoamorous can feel attraction to many different people, but only has one partner at a time. Unsolsexuals can only feel attraction to one person. One can be in relationships with other people despite not feeling attraction.
Unsolsexuals can change who the feel attraction to, but they can only feel attraction towards one person at a time. For example, they could feel attraction to only one person for a few months, but then if they began to feel attraction for another person, the attraction to the first person would go. Unsolsexuals usually hold attraction for one person for long periods of time, and not short.
Similar terms include unisexual.
Flag
The flag was designed when the term was coined, on October 12, 2020. The flag is the traditional four colors of the asexual flag, but lighter to show that it is a little more loose - and a strip of red was added to the bottom, red standing for love. The red was pastel however to indicate that the love is only for one person.
History
The term was coined by @-fierte on Scratch. The word 'unsolsexual' comes from the Latin terms 'unum solum' which translates roughly to 'only one'. The first letters, 'un' and 'sol' were taken and combined to form 'unsol'.