Thank for picking this up, even if it was just for this one chapter! Because it's totally worth reading and sharing.
I'm impressed by how much this manga "gets" how orientation works. Hormones contribute to a lot. Hormones do affect your brain. However your spiritual and emotional values are yours alone and are deeply tied into a physical component that isn't likely to just instantly change. What this actually makes you is still up to you in the end.
I've seen this happen with real life HRT -- some people do shift orientations, many don't. In truth none of us are 100% straight or gay to begin with and both hormones and circumstances and our own values all contribute to it. As an example, many of those who shift orientations probably already had a latent "gay" component that woke up when the hormones became available to it.
In any case, you don't have to worry about no longer being yourself. You only have to worry about becoming more yourself than you might've been comfortable with. I actually know some transgirls who became MORE into girls thanks to their new female hormones.