I usually find this to be the case unless the whole plot was designed for a literal harem end at the finish of the story. In 5toubun's case the whole set up from the 1st chapter, starting from the first panels with the unknown bride, to the chapter's ending with all sisters introduced and Fuutarou foreshadowing the chaos to come to the reader, is either a big fat red herring or just a teaser of something that would truly live up to the name of the title. More recently Negi has been dropping ambiguous hints as well but doesn't make it look like it's going to be ONE of the sisters, but possibly all of them, even though they are ambiguous teasers.We all know that In Japan harem ending is literally impossible with these types of stories it starts out "harem" ish but then gradually falls apart until the author decides who the ending chick is going to be and judging from all the past " harem" manga