What's the meaning behind this chapter or Mamoru's story? I kinda don't get if the story is related to his sister or something.
Late, but
"it is was really good"
Guess I am just too dumb to understand the depth of the story
The short of it is that the story of the manga that Mamoru drew plays to the strength of his artistic abilities. It is showing a set location in different phases. It is a "beautiful, well-maintained" garden transitioning to a poorly-maintained one. The implication is that something happened to the gardener, but that is intentionally left unanswered so that the one reading it can ponder the implications(subtext). It's likely meant to make the audience sad/melancholic/wistful (going for that "emotional" angle).
At least, that is idea behind it, as far as I can tell. It doesn't convey as well as it should, what with it only being a few panels that goes by too quick... and we can only assume so much from the art, what with it being in the manga's artstyle and all.
edit:
Elite NEET Mamoru chapter count:
3, 10, 192, 200, 248, 249, 250.4, 266.1, 273, 312, 326, 336, 378.3, 442, 472, 550, 551, 590, 614, 616.3, 669, 693, 733, 765,
Possibly 43, 57, 60, 79.7, 81(?), 116, 135, 181, 250.3, 264, 269, 274, 292, 340, 367, 383, 462.2, 473, 519, 544, 574, 613, 619, 623, 631.1, 640(Aki), 654, 679(?), 708, 717, 722, 760(?),
Worth mentioning, but doesn't count: 202, 205, 267, 301, 308.1, 317, 319, 412, 431, 432, 446, 452, 583(X), 586(X), 615, 617, 634, 656, 703, 709,
figured I would as this to the comment, rather than make a separate one