As the wedding day approaches, Tomie’s condition worsens. She begins to melt and emit a horrific stench, but she frantically tries to maintain her appearance and the illusion of happiness, terrified of being abandoned again. She begs Kenichi to love her despite her rotting state. In the end, the "Tomie" he fell in love with dissolves into a grotesque mass of flesh and hair, leaving Kenichi traumatized and his mother horrified, proving that Tomie can never escape her true nature, even when she sincerely wishes to.
To understand the joke (or the horror), we must revisit the source. According to the official Tomie wiki (and Junji Ito’s manga): tomie wants to get married wiki best
One possible interpretation of Tomie's desire to get married is that it stems from her desire for connection and intimacy. Despite her supernatural abilities and the chaos she often causes, Tomie seems to crave a sense of normalcy and stability that comes with a romantic partnership. Her desire to get married may be seen as a longing for a traditional and conventional life, which contrasts with the destructive and abnormal world she often creates. As the wedding day approaches, Tomie’s condition worsens
This is a where Tomie is portrayed as a college student who has lost interest in academics and seeks to marry a wealthy man to satisfy her vanity. In the end, the "Tomie" he fell in