If you're looking for a change of pace from Koenji's many crowded izakaya and craft-beer bars, Shimeji is a budget-friendly, old-fashioned pub-style bar. The interior is funky and unpretentious, with beer and liquor posters on the walls, a dartboard off in one corner, and a TV showing sporting events. Seating is comfortable and relatively spacious, and bouncy pop music plays in the background.
Cocktails and wines are very reasonable - bottles of wine start at around Y2500 - and simple dishes like pastas and jerk chicken offer good value for money. Scottish craft beers (Black Isle and Brew Dog) are available by the bottle if you're so inclined, and there are several Belgian beers as well.
Late-night hours are another attractive feature, especially if you've missed your last train - they're open until 6am most nights, and 7am on Fridays and Saturdays. Budget around Y2000-3000 for food and drink.