Most of the Reading Material from Rhythm Heaven Fever is either this or humorous. Highlights on the heartwarming side include:
"Partners" - See and Saw of Seesaw reminisce about how long they've been working together together (10 years!), apologize for their own mishaps and worry about each other's.
"My Feelings" - The protagonist of Double Date talks about learning to play guitar to impress his crush. He even wrote a song for her and has had trouble gathering the courage to play it for her... until the first soccer ball shows up and he kicks it.
"Picky Eaters' Song" - The Wandering Samurai of Samurai Slice remembers his mother.
"Expedition Journal" - The seal's trust in his captain despite the apparent nonsense of his orders is just touching.
About half the song lyrics.
"Final Words" - Some encouraging words involving a metaphor about fighting an evil wrestler army. Equal parts "Awww..." and "...what?"