In act 7, Usagi has just discovered that Mamoru is Tuxedo Kamen; he's wearing an unhappy expression because he's about to tell her about his dead parents. Obviously, this scene is still very early in the series. Mamoru's eyes are huge and his features take up a lot of his face, both making him look incredibly innocent and young. (He's supposed to be 17. Isn't he cute? Don't you just want to pet him on the head?) The fact that his mouth is set in a slight pout doesn't help him look any older. The eye is structured with the top eyelash stripe having only a slight curve, and a little thicker on one side. The eyeball is an almost perfect circle...

...which changes here. Now it's more of an oval, slightly squashed between the top and bottom lines of the eye. This makes him look older; the wide-eyed innocent young look from the first couple of acts is gone for good. Also, notice the bend in the top line of the eye. The way the lines of the eye curve around the eyeball makes his eyes look older and wiser; wise people don't have huge eyes, you see. Umm, this would be the middle of the Infinity arc, act 27; at this point, Chibiusa is being really cute in order to get Mamoru and Usagi to make her the holy chalice. What Mamoru's actually doing is showing off his knowledge of Communion and chalices...

Ahh, what I wouldn't give to have this guy leaning on the pillow beside me... *ahem* Anyway, this would be act 34, the beginning of the Dream arc. (Dead Moon.) His eyes are slightly narrowed because he's smiling; note, however, the sharper curve in the upper line of the eye, and the lengthening of the lower line. This trend is evident in all the characters as the series progresses. Now... look carefully at the part in his hair, and see how far it extends up his forehead. Then compare that distance to the distance in the first picture from act 7. There's a great deal more forehead visible... oh no! Could Mamo-chan's hairline be receding? Is our noble hero going bald? Say it ain't so!

<grin> ...kidding. Takeuchi-san wouldn't treat our hero like that. Besides, we know that Neo-King Endymion has all his hair even in the 30th century. Mamoru's just evolving under Takeuchi-san's pen, that's all. This is the very last act; in fact, it's the second-to-last page. Talking eye trends wouldn't really be fair here, because Mamoru's squinting into the sun to adore his beautiful new wife. However, take a look at the upper eye line. Note the sharp corner in the top right area of the closeup; this sort of abrupt corner became much more evident in the later volumes.