First, I want to say that Asami's gotten better looking over the years.
Second, it's not just you. Although Akihito's change is the most drastic, all characters have changed over time, which is to be expected from the same manga drawn by one artist for almost 19 years. Some of the differences are due to YA drawing everything in meticulous detail in the beginning, which took time to do (she's spoken about this). As she became more experienced, she learned how to streamline the process to produce more in less time.
Still, the effort began taking a toll on her drawing hand, so she's had to compensate for that. There's a lot less detail now when drawing the characters and she's employing the occasional SD (Super Deformed) style more and more-- the usage of which is very popular in anime and manga. Also, she's been progressively moving to be more in line with kawaii (Japanese cute culture) when portraying Akihito.
This last one has been controversial among fans-- mostly those who were initially drawn to the manga because in the early 2000's Akihito was unique for being a fairly masculine-looking uke character for that time. I miss that portrayal too, but the story and character building are good enough for me to not be too bothered by the change.
Does any one else think Akihito is starting to look more and more different in the later chapters? It looks like he's almost de-aging to me or something. Like in the last chapter he looks like a little kid haha. He looked so good and was so well drawn in the earlier chapters but now as the story progresses he just looks so different. Idk, it might just be me over thinking things as per usual lol. I love the story though and thanks for the updates<3