Perfect Formula for Love

Both are mini dramas in which the human FL encounters and becomes involved with a lonely deity with whom she falls in love. Both MLs vanish toward the end, then reappear in some way.

Although different in tone (DAYS is darker), both are about a human FL who makes a deal with/becomes involved with the ML who is a personification of something (math vs. doom). Both MLs are cold and distant at first but become sweet when they fall in love. The FLs end up living at/attached to the ML's house which is sort of cold and barren, reflecting their life. Both dramas have a scene of wishing on meteors.