As this is in Japanese, I just followed the charts, but have no idea what are the other written instructions.

Over-crochet to 19” on Pattern A (instead of 17” indicated on pattern), so instead of ripping, I just continue on. Scarfs still wears fine for me.

Might be a misprint on the chart of Row 1 of Pattern B:
At the end, pattern charts indicate: dc in previous dc, ch1, (dc, ch1, dc)-> in top of ch3 in previous row.
Correction I made: (dc, ch1, dc)-> in the same dc in previous, ch 1, dc in top of ch3 of previous row. This would match the beginning of Pattern B.

Attaching to Scarf:

1. Attach Motif A to the scarf using sc. (13 sc), leaving a long tail when
   attaching yarn to use for sew Motif B.
2. Continue to sc on the side (14 sc)
3. Sc 13 on bottom of motif
4. Sc 14 on the other side, join to 1st sc
5. Work edge fringe
6. Sl st 14 on side
7. Work edge fringe
8. Sl st 14 on the other side, join & fasten off.

Motif B - added another round of sc, leaving a long tail to sew to Motif A.

Edit: Link up pattern to Frill Mini Muffler