>>3983425ENTUM, or in full name ENTUM, Virtual Youtuber Office was a Vtuber agency. They were probably most known for being responsible for Mirai Akari and Nekomiya Hinata project but before their official opening they were involved with group composed of Eilene, Comdost, Yomemi, Moemi as early as in 2014.
Probably most notable person (besides Comdost who is known to be artfag on /a/) is Eilene who later contacter Deat (aka. Virtual Badass Deat) who was experimenting with 3D tracking systems and put groundwork for 3D Vtubing overall. Pretty much they were first relatively successful Vtuber group and without them we would not have any 3D events in the form we have now.
Also, if you want to know what they do now: Comdost is Comdost, Deat is still working on his Tracker World application and sometimes do streams to showcase new stuff and Eilene is Moe Natsumi.