Highway bus from Tokyo to Kawaguchiko

Hi, I'm planning to visit Kawaguchiko on 17 April.
I'm staying at Ikebukuro.

I'd like to ask what's the best mode of transport from Ikebukuro to Kawaguchiko and back, preferably with early departure from Ikebukuro and late departure from Kawaguchiko on the return leg?

Here is some of my own research:

I fiddled with the online reservation system on the Fujikyuko bus website. When I selected 17 April, I I could select the time slot for boarding at 06:05.
(It's this page: https://www.highwaybus.com/rs-web01-prd-rel/gp/foreign/frgSelectLine?l...)
However, according to their timetable http://bus-en.fujikyu.co.jp/highway/detail/id/1/#timetable 06:05 time slot is only applicable to weekends and holidays, am I right? 17 April is a Monday. So do I chalk it up to an error on the booking system?

I found a route on Japan Bus Online that does stop by Ikebukuro. Unfortunately, the last buses to Ikebukuro, or any part of central Tokyo, are ridiculously early (arrivals at 7plus) . I'm only doing a day trip so I'm hoping to be able to stay in Kawaguchiko until at least 7 plus, 8pm.
The Fujikyuko bus time table is decent enough, but I didn't like that they don't depart from Ikebukuro and their weird booking system discrepancy.

Any advice / recommendations are much appreciated!

If you don't mind returning to Shinjuku station or Tokyo station, then the last buses leave 6:40pm and 7:30pm, respectively.

From either Shinjuku or Tokyo station, it's just a train ride away to Ikebukuro.

There is one bus daily to and from Ikebukuro. http://bus.fujikyu.co.jp/highway/detail/id/8