This is the Filo arc. It isn't noticeable in the anime, but this volume is structured around Filo. She is the Arc Heroine, just like Raphatalia was in volume 1. Indeed, this volume follows a fundamentally similar structure.
At the start, Naofumi is mistreated by King Aultcray, who favors the other heroes over him. Then he acquires Filo and raises her while he does his adventurer-merchant thing. Spear Hero causes him trouble because of Princess Malty. Then a certain event occurs where he fears losing Filo, a Curse Shield activates, and Raphatalia brings him back to his senses. That is the bare-bones structure, and it is misleading.
This volume is very different from volume 1. Naofumi has developed as a person since the previous volume, and he has Raphtalia to soften his rough edges, so his interactions with others are different. The sense of despair and desperation that marked the first volume is not present here, because Naofumi is now an experienced hero and has a truly loyal party member.
Naofumi raises Filo from an egg, and so he truly is her father for all intents and purposes (aside from laying the egg himself). Filo is also a different character from Raphtalia, and the fact that she is even is a character at all, rather than a simple beast of burden, was a surprise to both Naofumi and Raphtalia.
Naofumi has advanced his trade beyond selling monster parts and is now a traveling apothecary. There's little detail on this but it is an interesting direction.
That's a thing about this volume. There is little detail given to things like Naofumi's trade or to the fights that he and his party engage in. The hostile plant encounter was really hard to follow, and the zombie-dragon likewise. The author seemed more interested in the emotional exchanges.
Trickster Eric Novels gives "Rising of the Shield Hero - light novel volume 2" a B+
Click here for my previous book review: Wandering Witch volume 2
Click here for my previous book review: I've been killing slimes for three hundred years and maxed out my level - light novel volume 3 (read for fun)
His fantasy series, Journey to Chaos, is currently available on Amazon as an ebook or paperback.