街に現れては様々な怪獣を倒して去る、という行動を繰り返す謎の怪獣・ネオメガス。カイザキ副隊長は、その真相を究明しようと奮闘するのだが、その中でかつての恩師の言葉を思い出す。
その言葉に秘められた恐るべき真実がカナタたちGUTS-SELECT、そしてウルトラマンデッカーの前に立ちはだかる！！
The mysterious monster Neomegas appears suddenly in town, defeats several other monsters, and leaves. Vice-Captain Kaizaki tries to find out what's really going out, when she remembers the words of her mentor. The terrifying true meaning behind those words reveals itself before Kanata, the GUTS-Select team, and Ultraman Decker!
