Katsuhiko Teshigawara

Katsuhiko Teshigawara (勅使河原 克彦) is a close friend of Mitsuha and Sayaka, as well as an expert with machinery; particularly explosives. He is a side character in the Kimi no Na wa. film.

Appearance
Tessie is a young man with an average build and height. He is slightly tanned, has thick dark eyebrows and a friendly smile. Tessie sports black hair which is kept distinctively shaved, and he has hazel-colored eyes. He was often depicted in his school uniform.

After the timeskip, Tessie has grown taller, developed a more muscular build, and it appears that he has grown a small stub.

Kimi no Na Wa
During the main story, it's pretty obvious that Tessie had a crush on Mitsuha. However, it is later shown during the alternate timeline that Taki and Mitsuha created that he and Sayaka are engaged. Tessie is not shown anywhere during the 2016 main story.

He, along with Sayaka, were the only people that helped Mitsuha with her plan to save the town people from the comet.

Epilogue (2021)
8 years after the comet, Tessie moved to Tokyo along with his friends, and presumably, his family. One evening, he and Sayaka are shown to be in a cafe which Taki also ended up in. They talk about their upcoming wedding while heckling each other, but leave before Taki can completely recognize them.

He with Sayaka were searching for a property to live in, In the end of the movie.

Trivia

 * In an interview, Makoto Shinkai revealed that Tessie is an image of his own childhood, as his parents were running a construction company and forced him to take over the business one day, just like Tessie in the movie.