Another possible theme could be self - discovery. In yaoi novels, the characters often go through a journey of understanding themselves better as they navigate their relationships. Also, acceptance, both self - acceptance and acceptance from others, might be important themes considering the nature of relationships in yaoi stories.
I'm sorry, I haven't read this specific 'all you need is love volume 1 yaoi novel' so I can't provide much detail. But generally, yaoi novels often focus on male - male relationships, exploring themes of love, friendship and personal growth within that context.
I'm not sure as I haven't read the novel specifically. But typically, in a novel with such a title, there might be a protagonist who is searching for love or learning about its true meaning. There could also be a love interest, and perhaps some supporting characters like friends or family members who influence the main character's journey regarding love.
The main theme is likely to be centered around the power of love. It might explore how love can overcome various obstacles, transform characters, and bring about positive change in their lives.
The main theme is likely love itself. It could explore different forms of love like romantic love, platonic love or love within a family. It might show how love can overcome difficulties and bring people together.
Without having read the 'love is all you need novel', it's difficult to name the specific main characters. But in a novel with such a title, we might expect to find a central character who is perhaps cynical about love at the start. Then there could be another character who comes into their life and changes their perspective on love. There might also be side characters like a wise old person who gives advice on love or a group of friends who support the main character's exploration of love.