Mitsukuni Shizuma (シズマ ミツクニ Shizuma Mitsukuni) is the founder of the Sizuma Foundation, and one of the key founding members of the TPU. In the Foundation's pursuit of space exploration and ancient alien research, he uncovers a looming, interstellar threat to mankind. In order to confront this menace, he united the governments of the world and established the TPU and the Expert Team GUTS-Select. But deep within his past hides an important secret.
Pre-Ultraman Trigger: New Generation Tiga
30 years before the beginning of the series, Mitsukuni was an intelligence officer working for TPC, and witnessed Ultraman Tiga save humanity many times over. One day, while investigating an area where unexplained mechanical problems occurred, his GUTS Wing malfunctioned and he fell into a time-space vortex, transporting him into Trigger's world. He eventually met Yurika who supported him in a strange and foreign world, and would become his wife. They had a child they named Yuna Shizuma, and were aware that, through her mother's lineage, she would be a descendant of Yuzare and may one day inherit an ancient destiny. Mitsukuni would then use his knowledge of the technology of his world to establish the Sizuma Foundation and subsequently, GUTS-Select.
Akito Hijiri was assigned by Mitsukuni Shizuma to replicate the Ancient Sparklence found in the Ultra-Ancient Ruins for the Giant of Light who he knows will eventually awaken, creating the GUTS Sparklence as a result.
Ultraman Trigger: New Generation Tiga
Shizuma went to Mars to accompany Kengo Manaka's mother, Reina Manaka, to a ruins site. They bear witness to a giant sword which has the same composition to another ruin site on Earth, confirming his suspicions that the Giants of Light were on Mars. When Golba is summoned by Carmeara to attack the site, Shizuma manages to drive it off using a GUTS Sparklence with a Gomora Kaiju Key inserted.
Running into a visibly distressed Kengo, he states his belief that everyone has a future they can dream of, and asks Kengo what his dream is. After hearing it, he says that there was one who fought bravely and paved their way to their own destiny - and that Kengo will have to find some answers on his own. He then hands over the GUTS Sparklence to Kengo, and with Reina, realizes that it was him that transformed into Ultraman Trigger afterwards.
From a safe distance, he and the rest of the Mars Development Division crew watch the Ultra's battle with Carmeara and Golba. After Trigger's victory, Shizuma invites Kengo to be an official member of GUTS-Select.