As the two Seras hands touched, a searing pain scorched both souls. They wanted to scream at the top of their lungs, but they had lost control over their bodies.
Their hands stayed in contact and slowly melted into each other. Seconds, or perhaps an eternity passed, it was impossible to tell, but at some point, the hands fully melted together.
The pain only worsened thereafter. Where their hands once were, now an inevitable, strong pulling force, grabbed hold of both souls. In a rather crude way, their bodies slowly became formless.
The force continued pulling. Their arms melted together, then their other hands, and eventually their legs and lower bodies.
When their chests started turning formless, the pain became a thousand times worse. A shriek left both of their mouths containing the worst pain imaginable.
The pull hadn't slowed even a little, but after their chests became formless, the pain lessened quite a bit. They hardly felt it when their heads finally connected.