Happoshu is a type of beer in Japan that denotes low-malt, 67% to be exact according to Japanese law. Happoshu is a Japanese word that means sparkling spirit in English, but without the association to sparkling wine. Rather lower malt beer has great flavor is a matter of personal opinion, but if you were to judge it by its color, head, texture, and aroma, then one could argue that full malt beers win over low malt beers because of the broader range of tasting profiles in full malt beers. People drink Happoshu in Japan because it's cheap and has just enough alcohol to get you drunk, while still maintaining a fairly decent flavor.
Asahi's "Off," is another top very low-calorie beer in Japan. It pour a gold color. Nose is weak. It really doesn't have much taste for me, but after taking one sip I was slightly disappointed. However, some of my colleagues claim that the beer is light tasting and refreshingly clean on the palate. Easy to drink and enjoy without getting too drunk, so not too bad of a choice, I think. Still quite popular with Japanese.
Third sector beers take happoshu and blend it with spirits derived from barley or wheat. Some have low-calories, others have zero glucose content, while others contain less additives and purines. Alcohol content in these drinks ranges from 4% to 8%.
Kirin Tanrei Green Label by Kirin pours a pale yellow colour, no head. Smells malty. Not a bad beer, nothing special, though. It has a great flavor depending on who's drinking it. Typically, Westerners may not identify with the same flavor profiles as Japanese drinkers on this particular beer. This is still considered a popular low-calorie beer in Tokyo.
Aqua Blue (Asahi) pours a pale straw color. It has a decent white head and is full strength with low-calories. This beer is popular with binge drinkers who want something light for dinner while still enjoying a fairly decent alcohol percentage.
Kirin ZERO (Kirin) pours a pale yellow. The foam head dissipates rather quickly. Faint aroma of pale malt. Tastes like watered down beer, faint hints of wood. Not much going on, but not bad. Again, finding a great tasting low-calorie beer is a matter of personal tastes and preferences. When you replace malt with spirits or other additives, you get less beer characteristics.