I think that takeru should end up with both Haruko and Inaho. He would mainly be married to Haruko, but she will also be willing to share Takeru with Inaho both romantically and sexually. She's become like a sister to her, and she loves Inaho very much. That's why she felt guilty after hearing Takeru reject Inaho knowing it was because of her. It would be like the harem plan in to Love Ru anime.
How do you guys feel about this ending idea?
Takeru does clearly have some romantic feelings for Inaho as well. Not as much as Haruko but still a little. He probably only rejected her because he was still unsure about his situation And wasn't ready to make that choice yet.