"Model Suit Gunpla Builders Beginning G" is a short anime series set in a world where Gunpla (Gundam plastic models) building and battling have become a popular hobby. The story centers on Haru Irei, a young boy who discovers a passion for Gunpla after encountering a rare model, the Beginning Gundam, at a hobby shop. Inspired by the intricate design and potential of the model, Haru begins building and customizing it, eventually entering the competitive world of Gunpla battles.

The narrative explores Haru's journey as he learns the intricacies of Gunpla construction and combat. Along the way, he meets other enthusiasts, including Rina Noyama, a skilled builder who becomes his rival and later his ally, and Kenta Sakazaki, a cheerful and supportive friend who shares his enthusiasm for Gunpla. Together, they participate in various battles, honing their skills and strategies while facing off against formidable opponents.

The series emphasizes the creativity and dedication required to excel in Gunpla building and battling. Haru's Beginning Gundam undergoes several modifications throughout the story, showcasing the importance of innovation and adaptability in the competitive scene. The battles themselves are depicted as immersive simulations, where the models come to life in virtual arenas, allowing builders to test their craftsmanship and tactical prowess.

As the story progresses, Haru and his friends encounter stronger opponents, including the enigmatic and highly skilled Tatsuya Yuuki, who challenges Haru to push his limits. The series culminates in a high-stakes tournament where Haru must rely on his growing skills and the bonds he has formed with his friends to achieve victory. Through these experiences, Haru not only becomes a more proficient builder and battler but also gains a deeper appreciation for the Gunpla community and the friendships it fosters.