The official line is that hours follow the host Edion store, and Edion AKIBA runs 10:00-20:00 on weekdays, weekends and holidays alike. The official page states that the buyback desk closes earlier than the shop, and a card directory notes irregular closures.
On Chuo-dori just south of Onoden, the large building under the blue EDION signs. Enter through the main electronics entrance and take the lift to 6F; the card shop sits next to Edion's own Mini 4WD circuit. It is a different shop from the trading-card malls on B1F and 5F of the same building, so do not confuse the floors.
Tips
A trading-card chain run by Edion itself, and the only branch in Tokyo on its official store list. Titles handled include Pokemon, Yu-Gi-Oh, Duel Masters, Battle Spirits, Vanguard, Weiss Schwarz and Union Arena.
There is a free duel space and a counter buyback service; buyback intake closes earlier than the shop itself.
Besides cash, credit cards and QR payments are accepted, and V Points, d Points and R Points can be earned or spent.
Some directories wrongly print 1F, but the shop's own X account puts it on 6F - take the lift in the electronics store up to the sixth floor.