Complex sentence: The other Tarōs do the same with Diend's summoned Riders while Deneb enters Kotaro, enabling Kamen Rider New Den-O to assume Vega Form.
Split into simpler sentences: The other Tarōs do the same with Diend's summoned Riders. Deneb joins the fray by entering Kotaro, enabling Kamen Rider New Den-O to assume Vega Form.