After using exkifint and hgx2bmp to extract スズノネセブン! and スズノネセブン!-Sweet Lovers' Concerto-, I could not find out the eyecatch images that are shown in those games from the extracted images.
I noticed that eyecatch_02.hg3(1.1M), eyecatch_03.hg3(607K) and eyecatch_04.hg3(585K) were converted to exactly the same image. It is a logo showing the game's tilte, but not the eyecatch image.
I believe that eyecatch_xx.hg3 contains both the logo and the eyecatch image, but it seems that hgx2bmp cannot extract all frames/images/layers in hg3 images extracted from スズノネセブン! and スズノネセブン!-Sweet Lovers' Concerto-.
Can you take a look at this?