Sirena represents the Italian dub name for Shūta Gō, known as Siren in English-Malay and Russian dubs. This 13-year-old Japanese boy from Nagano leads an ordinary life as a student and soccer player until Decepticons attack his father's observatory. Witnessing Professor Gō's fatal wounding in this assault propels Shūta into the Autobot Pretenders' conflict. Recruited by Autobot Pretender Metalhawk, he gains Master-Braces enhancing his physical abilities with Chōkon Power and bonds with a Transtector from Master. This fusion transforms him into the Headmaster Junior "Go Shooter," merging with a Toyota Supra police car Transtector into a robotic form wielding a Plasma Power Rifle and Plasma Gun.

Characterized by enthusiasm, a strong sense of justice, and impulsiveness often leading him into peril, Shūta forges friendly rivalries and bonds with fellow Headmaster Juniors Cab and Minerva, sharing mutual affections. He actively participates in battles against Devil Z and the Decepticons alongside Autobot Godmasters. Key actions include spearheading the reactivation of Grand Maximus's tachyon converter during atmospheric re-entry using a rocket pack, a near-fatal act saving the ship. Later captured by Overlord as bait for Ginrai, he is rescued by the defecting Decepticon Cancer. During the final clash against Devil Z-possessed BlackZarak, he and the other Headmaster Juniors channel their combined Chōkon Power into God Ginrai's decisive "Final Fire Guts" attack, destroying Devil Z.

Following Devil Z's defeat, the bond between humans and Transtectors severs. The Transtectors, having gained sentience through their partnerships, attain independent life. Go Shooter's Transtector retains the name and departs into space with other newly sentient Transformers to hunt remaining Decepticons, while Shūta returns to his human existence on Earth.